,,.'   "«**'""  " 'j|. 
WATER  SUPPLY. 


W,  H,  CORFIELD,  ESQ.,  I,  A,,  M,  D, 

Y(  (OXON.) 

PROFESSOR  OF  HYGIENE  AND  PUBLIC  HEALTH  AT  UNIVER- 
SITY   COLLEGE,    LONDON  ;    MEDICAL    FELLOW    OF 
PEMBROKE  COLLEGE,  OXFORD;  AND  MEDI- 
CAL OFFICER  OF  HEALTH  AT  ST. 
GEORGE'S,  HANOVER  SQUARE. 

SECOND    AMERICAN    EDITION. 


NEW    YOEK: 

D.  VAN  N08TRAND  COMPANY, 

23  MURRAY  AND  27  WARREN  STREET. 

1890. 


UHITBRSITY 


PREFACE 

TO 

SECOND  AMEEICAN  EDITION. 

The  first  edition  of  the  abstract  of 
these  Lectures  *appe&r£d  in  Yan  Nos- 
trand's  Engineering  Magazine  in  1875, 
and  subsequently  were  incorporated  in 
the  Science  Series,  for  the  reason  that 
at  that  time  there  was  a  demand  for 
monographs  on  this  special  subject,  the 
literature  at  that  period  being  somewhat 
scanty. 

The  original  Lectures  were  delivered  at 
the  School  of  Military  Engineering, 
Chatham,  England,  in  the  autumn  ses- 
sion of  1873,  and  were  subsequently 
printed  for  private  circulation,  and  at- 
tracted by  their  clearness  and  concise- 
ness in  detail,  a  very  wide  attention. 


The  principal  point  in  view  by  Prof. 
Corfield  was  public  health,  and  in  this 
respect  he  did  not  enter  into  engineering 
matters  to  any  great  extent,  not  more  so 
than  the  subject  absolutely  required,  but 
he  went  very  thoroughly  over  the  whole 
ground,  treating  it  in  a  practical,  com- 
mon-sense view.  For  these  reasons, 
and  from  the  fact  that  a  very  great  many 
publications  bearing  upon  this  subject 
have  appeared  since  these  Lectures  were 
printed,  it  has  been  deemed  advisable,  as 
the  publishers  desire  to  keep  the  differ- 
ent numbers  of  this  Series  available  to 
the  public,  to  reprint  this  particular  one 
without  change  or  addition,  the  fact 
being  that  comparatively  little  if  any 
changes  or  additions  could  add  to  the 
permanent  value  of  the  matter  presented 
in  these  pages.  The  Lecture  form  has 
been  preserved  throughout.  Prof.  Cor- 
field's  further  Lectures  on  "  Sewerage 
and  Sewage  Utilization"  form  No.  18  of 
this  Series.  W.  H.  F. 

NEW  YORK,  December,  1889. 


WATER  AP  WATER  SUPPLY. 


It  will  be  our  purpose  to  discuss,  in 
the  first  place,  the  sources  and  the  kind 
of  water  that  are  required  for  large  com- 
munities— the  kind  in  the  first  place,  the 
quantity  in  the  next,  the  places  to  get  it 
in  the  third,  and  then  the  ways  to  con- 
vey it  to  the  community. 

It  is  only  one  part  of  the  fuel  of  a 
community  that  we  have  to  consider. 
We  shall  then  consider  what  are  the 
wastes  from  a  large  community,  and 
whether,  although  useless  for  the  pur- 
pose for  which  the  original  fuel  was  sup- 
plied, they  can  be  made  useful  for  other 
purposes,  and  if  so,  how?  Whether 
again  there  is  any  necessity  of  getting 
rid  of  them,  and  if  so,  how  this  can  be 


,6 

clone  most  effectually,  and  most  cheaply, 
rind  w.itTiout;  prejudice  to  other   commu- 
"nities. 

Now  then  as  regards  water.  Water  is 
required  in  a  large  community  for  a 
great  variety  of  uses.  These  uses  were 
divided  by  the  Eomans,  and  they  have 
been  divided  ever  since,  into  public  and 
private  uses.  The  public  uses  are  such 
as  for  cleaning  streets,  extinguishing 
fires,  for  fountains,  for  public  baths,  and 
so  on.  The  private  uses  are  for  drinking, 
washing,  cooking,  etc.  Thus  water  you 
see  at  once  from  the  mere  examination  of 
its  uses  comes  to  the  community  to  be 
soiled.  It  comes  in  order  that  the  com- 
munity may  be  supplied  with  one  of  the 
necessities  of  life.  It  comes  to  wash 
communities,  places,  and  habitations.  It 
comes,  I  repeat,  to  be  soiled.  It  is, 
therefore,  generally,  when  soiled,  useless 
for  the  purpose  it  was  originally  wanted 
for.  It  has  either  to  be  purified  or  got 
rid  of.  A  community  requires  pure  water 
for  some  purposes,  and  those  are  especial- 
ly for  drinking  and  cooking.  Pure  water 


— I  do  not  mean  chemically  pure,  but  we 
shall  see  directly  what  is  meant  hygieni- 
cally  by  pure  water — is  not  necessary  for 
every  purpose,  such  as  for  washing  the 
streets,  extinguishing  fires,  etc.  How- 
ever, practically  speaking,  only  one  kind 
of  water  can,  as  a  rule,  be  supplied  to  a 
community,  and  so  it  becomes  necessary 
for  us  to  know  where  we  can  get  this 
sufficient  supply  of  water  of  a  certain 
quality,  viz.,  sufficiently  good  for  drink- 
ing. 

Now,  roughly  speaking,  a  drinking 
water  should  be,  in  the  first  place,  trans- 
parent. In  the  second  place,  it  should 
be  transparent  to  white  light ;  that  is  to 
say,  it  should  be  transparent  and  with- 
out color.  It  must  be  without  taste  and 
without  smell,  and  it  must  deposit  no 
sediment  on  standing,  and  have  no  par- 
ticles suspended  in  it.  Those  are  the 
rough  qualities  of  water  which  anybody 
can  examine  for  himself  ;  the  best  way  to 
look  at  it  is  to  look  through  about  a  foot 
or  18  inches  of  it  in  a  long  glass  cylinder, 
placed  on  a  piece  of  white  paper.  It 


8 

must  be  aerated  to  be  fit  for  drinking, 
and  cool.  Now,  if  the  water  you  are 
examining  does  not  fulfill  these  condi- 
tions, it  must  be  rejected  at  once,  or 
brought  to  satisfy  them.  We  have  to 
consider  how  these  conditions  are  to  be 
fulfilled,  and  we  ought  to  satisfy  them 
on  a  large  scale.  But  a  water  may  com- 
ply with  all  these  conditions,  and  yet  not 
be  a  safe  water  to  drink.  It  may  contain 
substances  which  you  cannot  tell  in*  any 
of  these  ways,  and,  practically  speaking, 
all  waters  do.  Substances  whether  in 
solution  or  suspension  may  be  hurtful,  or 
they  may  be  harmless;  and  now  I  want  to 
tell  you  how,  if  you  have  a  chemical 
analysis  of  a  sample  of  water  before  you, 
you  can  tell  whether  that  water  is  suita- 
ble for  your  purpose  or  not.  That  is  a 
thing  you  do  not  generally  find  in  engi- 
neering books.  It  is  necessary  for  you  to 
know  it,  because  if  a  report  is  brought 
up  upon  a  particular  water,  you  ought 
to  be  able  to  know  whether  that  will  be 
a  satisfactory  water  or  not. 

Natural  waters   contain    dissolved  (in 


the  first  place  especially)  carbonic  acid 
gas.  They  contain  all  the  constituents 
of  air  in  solution,  but  the  gases  are  not 
in  the  proportion  in  which  they  are  in 
atmospheric  air.  There  is  often  a  great 
quantity  of  carbonic  acid  gas,  and  oxygen, 
being  more  soluble  than  nitrogen,  is 
generally  in  larger  proportion  than  in 
atmospheric  air.  Now  the  carbonic  acid 
gas  is  the  one  that  I  am  going  to  speak 
of  first.  Water  containing  carbonic  acid 
in  solution  has  the  property  of  holding 
in  solution  quantities  of  certain  salts  that 
it  would  not  dissolve  otherwise,  or  only 
in  much  smaller  quantities,  and  the 
chief  of  these  is  carbonate  of  lime. 
Natural  waters  often  contain,  then,  in  the 
first  place,  salts  of  lime,  especially  the 
carbonate,  dissolved  in  carbonic  acid. 
They  contain  often  the  sulphates  of  lime, 
soda,  magnesia,  iron,  and  so  on — in  fact, 
different  salts  of  these  and  other  bases. 
Phosphates  they  all  contain,  and  also 
chlorides  and  nitrates.  All  natural 
waters  contain  the  latter  in  certain  pro- 
portions— even  rain  water.  Almost  all 


10 


of  them  contain  salts  of  ammonia.  The 
question  arises  which  of  these  may  be 
allowed  in  water,  and  which  may  not,  or 
which,  at  any  rate,  may  not  be  allowed 
above  a  certain  quantity,  and  what  is 
the  quantity?  Beyond  those  simple 
characters  for  pure  water  which  I 
gave  you  a  few  minutes  ago,  there  is  a 
property  of  natural  waters  which  can  be 
easily  ascertained  by  any  one,  and  which 
constitutes  one  of  the  best  known  differ- 
ences between  various  specimens  of 
water,  and  that  is  the  quality  of  hardness. 
What  does  that  mean?  Hardness  is 
tested  in  this  way.  Pure  water  dissolves 
soap,  which  is  a  combination  of  soda 
with  some  of  the  fatty  acids.  Pure  water 
dissolves  soap  perfectly  and  forms  a 
lather  at  once.  Now  water  containing 
certain  salts  in  solution,  and  notably 
salts  of  lime,  magnesia,  and  iron,  does 
not  do  so,  because  these  salts  form  in- 
soluble precipitates  with  the  soap.  That 
is  what  is  meant  by  the  water  being  hard. 
If  a  water,  instead  of  lathering  with  soap 
immediately,  takes  a  great  deal  of 


11 

trouble  to  make  a  lather,  does  not  do  it 
till  after  some  time,  and  causes  a  curdy 
precipitate,  then  it  is  a  hard  water. 
That  is,  of  course,  a  very  rough  way  of 
putting  it ;  but  the  amount  of  soap  that 
is  required  before  a  water  will  lather, 
gives  a  test  of  the  amount  of  salts  which 
cause  the  hardness  of  the  water,  and  the 
chemist  takes  a  standard  solution  of 
soap  and  tries  how  much  of  this  solution 
is  required  before  he  can  get  a  lather 
with  water,  and  he  says  that  the  water 
has  so  many  degrees  of  hardness.  What 
is  meant  by  a  degree  of  hardness  1  That 
each  gallon  of  the  water  contains  in  so- 
lution an  amount  of  salts  which  will  pre- 
cipitate as  much  soap  as  a  grain  of  car- 
bonate of  lime  would  precipitate.  What 
is  the  importance  of  this?  Hard  water 
is  as  a  general  rule  less  wholesome  than 
soft,  and  often  much  less  so,  it  is  not  so 
good  for  household  purposes,  nor  for 
use  in  engines,  and  it  entails  an  enormous 
waste  of  soap.  It  is  therefore  objection- 
able, even  if  the  hardness  is  caused  by 
the  presence  of  harmless  salts.  The 


12 

total  amount  of  hardness,  the  degree  of 
hardness  of  a  water  before  anything  is 
done  to  it,  is  called  the  "  total  hardness," 
and  if  the  total  hardness  of  a  water  is 
greater  than  six  degrees  on  what  is  called 
"  Clark's  Scale  "  (the  value  of  a  degree 
of  which  I  have  already  explained)  it  is 
called  a  hard  water  ;  if  less,  it  is  known 
as  a  soft  water.  Now  hard  water  (sup- 
posing you  have  only  got  hard  water, 
and  cannot  get  a  supply  of  soft  water)  is 
made  softer,  in  the  first  place,  by  boiling. 
That  can  be  done  on  a  small  scale.  If 
you  boil  hard  water,  of  course  the  car- 
bonic acid  is  driven  off,  and  the  salts 
held  in  solution  by  it,  especially  carbon- 
ate of  lime,  are  precipitated.  There  is 
another  way  of  rendering  hard  water 
soft,  and  this  can  be  applied  on  a  large 
scale  ;  it  is  known  as  "  Clark's  process." 
The  carbonate  of  lime  is  held  in  solution 
in  the  water  by  carbonic  acid ;  you  can 
precipitate  it  by  boiling,  or  prevent  its 
being  held  in  solution  by  causing  the 
carbonic  acid  to  combine  with  something 
else,  as  with  more  lime,  and  Clark's  pro- 


13 

cess,  which  is  now  used  on  an  extensive 
scale  (and  ought  to  be  used  very  much 
more  than  it  is)  consists  in  adding  to  the 
hard  water  milk  of  lime.  This  milk  of 
lime  combines  with  the  excess  of  car- 
bonic acid,  forming  carbonate  of  lime, 
which  falls  down  as  precipitate  together 
with  the  carbonate  of  lime  that  was  pre- 
viously held  in  solution,  thus  leaving  the 
water  softer.  If  you  boil  water,  and 
then  determine  the  hardness  that  remains, 
that  is  called  the  "  permanent  hardness''; 
an  extremely  important  matter.  The 
importance  of  it  consists  in  this,  that  it 
cannot  be  removed  at  any  rate  on  a  large 
scale,  and,  in  the  second  place,  that  it  is 
due  to  salts  several  of  which  are  injuri- 
ous, so  that  a  large  degree  of  permanent 
hardness  indicates  a  bad  water.  Now 
this  permanent  hardness  (the  hardness 
that  is  lost  by  boiling  is  called  u  tempo- 
rary hardness")  is  due  chiefly  to  the  sul- 
phate of  lime  and  chloride  of  calcium, 
and  to  magnesian  salts.  These  are  all 
objectionable  in  a  water.  Let  me  give 
you  some  examples  of  degrees  of  hard- 


14 

ness  of  various  specimens  of  water  so  as 
to  give  you  a  definite  idea  of  hard- 
ness. 

The  hardness  of  the  Thames  water 
above  London  is  14  degrees  of  Clark's 
scale.  That  is  a  hard  water.  The  hard- 
ness of  the  New  Kiver  water  is  15^  de- 
grees. That,  too,  is  a  hard  water.  The 
water  of  Bala  Lake  has  only  J  of  a  de- 
gree of  hardness,  and  of  course  that  is 
an  exceedingly  soft  water.  I  must  tell 
you  before  going  on  that  it  is  now  very 
usual  to  express  hardness  in  another  way. 
That  is  to  say,  instead  of  saying  so  many 
grains  per  gallon,  as  is  done  in  Clark's 
scale,  hardness  is  now  very  generally  ex- 
pressed by  parts  in  100,000,  and  I  men- 
tion this  at  once,  because  the  results  of 
most  of  the  analyses  that  we  shall  have 
to  refer  to  during  the  lectures  are  given 
in  parts  per  100,000.  Of  course,  if  you 
are  given  the  hardness  of  water  in  parts 
per  100,000,  you  can  convert  it  into  de- 
gress of  hardness  in  Clark's  scale  by 
multiplying  by  seven  and  dividing  by 
ten,  because  Clark's  scale  gives  the  re- 


15 

sul  s  in  grains  per  gallon;  a  grain  per 
gallon  is  one  part  in  70,000.  On  this 
new  scale,  as  an  example,  the  hardness 
for  the  last  week  of  last  year  of  the  five 
Thames  companies  was  about  20  de- 
grees, that  is  to  say,  about  14  degrees 
by  Clark's  scale. 

The  hardness,  again,  of  the  water  sup- 
ply which  is  derived  from  deep  borings 
in  the  chalk  was  29.4  on  this  scale,  or 
20.58  of  Clark's  scale.  Of  course  that 
is  a  very  hard  water  indeed.  But  the 
hardness  of  these  two  waters  is  quite 
different,  because  the  permanent  hard- 
ness of  Kent  water  is  very  little  indeed. 
The  total  hardness  of  that  water  is  al- 
most entirely  due  to  the  carbonate  of 
lime,  whereas,  much  of  the  hardness  of 
the  water  supply  to  London  by  the 
Thames  companies  is  due  to  salts  other 
than  carbonates,  especially  to  sulphates. 
Therefore,  you  get  much  information 
about  the  quality  of  water  by  its  hard- 
ness. If  you  know  water  has  a  high  de- 
gree of  permanent  hardness,  you  know 
it  has  a  very  good  chance  of  being  a  bad 


16 

water.  It  contains  probably  sulphate  of 
lime  and  chloride  of  calcium,  and  per- 
haps magnesian  salts.  The  latter  are 
especially  objectionable  to  water,  and 
any  water  which  gives  even  a  small 
amount  of  salts  of  magnesia  is  to  be  re- 
jected. Water  containing  these  salts 
causes  diarrhoea  when  drunk,  and  it  ap- 
pears to  be  from  the  presence  of  these 
salts  in  drinking  waters  that  the  swelling 
of  the  neck  known  as  goitre  is  produced 
in  Switzerland  and  other  countries. 

The  next  thing  to  which  I  wish  to 
draw  your  attention  with  regard  to  sub- 
stances dissolved  in  water,  is,  the  amount 
of  chlorides  that  may  be  present.  I  may 
say  broadly,  that  if  you  see  in  a  report 
on  the  quality  of  a  water  that  it  contains 
much  chlorine,  or  much  common  salt 
(chloride  of  sodium),  you  may  at  once 
put  it  down  as  a  suspicious  water,  and 
you  will  see  why  in  a  minute.  Where 
do  you  get  chlorides  in  a  water  ?  They 
may  come  from  an  infiltration  from  the 
sea.  They  may  come  again  from  strata 
containing  a  quantity  of  common  salt. 


17 

Bat  another  source  of  chlorides  in  a 
water  is  pollution  by  sewage.  All  sewage 
contains  a  considerable  proportion  of 
common  salt.  This  is  one  of  the  necessi- 
ties of  life,  it  is  contained  in  many  of 
our  foods,  and  in  excretal  matters, 
especially  in  the  urine,  and  so  sewage 
contains  it.  The  average  amount  in  the 
sewage  of  water-closeted  towns  is  ten 
parts  of  chlorine  in  the  100,000.  Pure 
natural  waters  contain  less  than  a  grain 
of  chlorine  in  a  gallon,  or  about  1  part 
in  100,000.  So,  if  in  a  sample  of  water 
for  which  you  get  the  analysis  sent,  you 
see  more  than  a  grain  in  a  gallon  of 
chlorides,  you  must  at  once  know  the 
reason  why.  London  drinking  water 
contains  2  parts  in  100,000.  That  is  not 
very  bad  water,  and  as  it  is  got  from  the 
Thames  we  know  that  it  has  been  pol- 
luted by  sewage.  The  water  derived 
from  the  chalk — the  Kent  water — actu- 
ally contains  more  than  that,  but  we 
have  a  very  good  reason  for  not  object- 
ing to  it  on  that  account,  inasmuch  as 
we  know  that  it  is  not  rendered  impure 


18 

by  sewage.  The  well  waters  of  London 
mostly  contain  more  chlorine  than  sew- 
age; they  are,  in  fact,  a  concentrated 
form  of  sewage  which  has  gone  through 
certain  alterations.  I  am  not  here  allud- 
ing to  the  Artesian  Wells,  but  only  to 
those  which  are  supplied  by  the  subsoil 
water  above  the  London  clay.  The 
amount  of  chlorine  is  a  very  good  test 
of  the  purity  of  a  water,  except  that 
you  must  always  allow  for  the  possibil- 
ity of  chlorides  being  present  in  the  soil 
through  which  that  water  has  gone. 

Nitrates  and  nitrites  are  given  you  in 
the  Registrar  General's  Reports  as  the 
test  for  what  is  called  "pre&iou*  sewage 
contamination."  What  does  that  mean  ? 
It  means  that  the  nitrates,  etc.,  that  are 
dissolved  in  water  come  in  a  great  major- 
ity of  cases  (if  not  in  all)  from  the  oxyda- 
tion  of  organic  matter  at  some  time  or 
other,  or  in  some  place.  Now  to  show 
you  how  plain  it  is  that  water  must  not 
be  rejected  merely  because  it  contains 
nitrates,  I  must  tell  you  that  there  are 
nitrates  and  nitrites  in  all  waters,  even 


19 


in  small  quantities  in  rain  water.  What 
amount  of  nitrates  may  be  found  in 
water  without  giving  a  suspicion  of  pre- 
vious contamination?  Allowing  that 
they  are  not  injurious  in  themselves,  yet, 
inasmuch  as  they  at  once  make  you  sus- 
pect that  the  water  containing  them  in 
solution  has,  at  some  time  or  other,  been 
contaminated  with  organic  matters  to  a 
large  extent,  which  organic  matters  have 
been  oxydized,  the  result  being  the  pro- 
duction of  nitrates  and  nitrites — inas- 
much as  that  is  the  case,  if  you  get 
much  nitrates,  etc.,  represented  in  a 
water,  you  must  at  once  see  if  that  water 
is  derived  from  a  source  where  it  is  likely 
to  get  contaminated  with  refuse  matters; 
because  if  it  is,  although  the  nitrates 
are  harmless,  and  although  it  is  very 
desirable  that  these  matters  should  be 
oxydized  to  that  state,  still  you  are  al- 
ways liable  to  its  happening  some  day 
that  the  water  is  contaminated  by  the 
solution  of  these  organic  matters  in  their 
crude  un oxydized  form,  in  which  case 
they  are  very  often,  if  not  always,  danger- 


20 

ous.  Let  us  see  what  amount  of  nitrates 
is  found  in  various  waters.  In  the  drink- 
ing water  we  get  in  London  from  the 
Thames  there  are  about  2  parts  in  a  mil- 
lion (or  0.2  in  100,000).  In  the  New 
River  Water  (North  London  water)  a 
little  more  than  3  parts;  and  in  the 
Kent  water  4  parts  in  a  million,  so  that 
the  deep  chalk  waters  (which  we  know 
must  be  very  pure)  contain  more  nitrates 
than  the  others  do,  a  sufficient  proof 
that  the  presence  of  nitrates  is  not  of 
itself  a  sufficient  reason  for  rejecting  a 
water.  The  waters  from  the  Cumber- 
land Lakes  contain  very  much  less.  To 
give  you  an  example  of  a  water  contain- 
ing a  great  deal,  I  may  cite  the  instance 
of  a  well  at  Liverpool  which  was  found 
to  contain  more  than  8  parts  in  100,000 
of  nitrates  and  nitrites,  which  were  all 
derived  (or  in  all  probability  derived) 
from  the  oxydation  of  sewage  that  had 
traversed  the  ground  round  that  well. 
If  nitrates  be  present  in  large  quantities 
it  must  be  regarded  as  a  suspicious  cir- 
cumstance, unless  you  have  good  reason 


21 

to  know  that  the  water  comes  from  a 
source  which  is  beyond  the  suspicion  of 
contamination.  There  are  quantities  of 
nitrates  in  many  soils.  The  presence  of 
nitrates  in  water  got  from  such  soils 
would  not  justify  you  in  having  the 
water  condemned  as  a  source  of  supply 
if  there  were  no  other  reason. 

Salts  of  ammonia.  These,  too,  are 
contained  in  natural  waters  in  exceed- 
ingly small  quantities.  They  do  no 
particular  harm  in  themselves,  but  they 
frequently  come  directly  from  sewage. 
The  numbers  in  a  drinking  water  repre- 
senting salts  of  ammonia  ought  to  be  in 
the  third  place  of  decimals  for  parts  in 
100,000,  or,  if  in  the  second  place  of  dec- 
imals, ought  to  be  small.  Now  the  water 
supply  of  London,  filtered  Thames  water, 
contains  .001  to  .005  parts  in  100,000. 
That  is  pretty  good.  The  water  at  Bala 
Lake  con  tains  .001  parts,  and  rain  water 
contains  the  same  amount ;  so  that  we 
may  expect  salts  of  ammonia  to  be  con- 
tained in  all  natural  waters.  Sewage 
contains  about  6  parts  in  100,000.  Well 


22 

water  often  contains  large  quantities, 
four  parts,  for  instance;  the  pump  water 
in  London  contains  nearly  one  part  in 
100,000,  and  the  water  of  the  Thames  at 
London  Bridge  0.1  part  in  100,000;  these 
are  all  bad  waters,  so  that  when  you  see 
ammonia  mentioned  in  an  analysis  of 
water  in  greater  quantity  than  is  repre- 
sented on  the  second  place  of  decimals  in 
parts  per  100,000,  you  may  always  safely 
condemn  it,  for  on  looking  further  you 
will  find  what  I  am  now  going  to  speak 
of,  namely,  organic  matters. 

Now  the  actual  organic  matters  pres- 
ent in  a  water  may  be  in  suspension  or 
solution.  If  there  are  organic  matters 
in  suspension  a  water  may  be  safely  con- 
demned, because  they  may  even  by  agi- 
tation pass  into  solution,  and  so  the  fact 
of  your  trying  to  separate  them  may 
cause  more  of  them  to  get  into  solution. 
Organic  matters  you  will  find  in  analysis 
represented  in  two  different  ways.  In 
one,  as,  for  instance,  in  the  analysis  given 
by  the  Registrar  General,  you  will  find 
organic  matters  represented  in  this  way : 


23 

so  much  organic  carbon,  and  so  much 
organic  nitrogen  in  the  100,000,  and  the 
Eivers  Pollution  Commissioners  have 
given  this  as  a  standard,  not  of  drinking 
water,  but  of  a  water  that  shall  be  con- 
sidered to  pollute  any  watercourse  to 
which  it  is  turned.  Two  parts  of  organic 
carbon  in  100,000  or  3  parts  of  organic 
nitrogen  in  100,000.  What  does  the 
London  drinking  water  contain  again? 
From  3  to  4  in  100,000  of  organic  car- 
bon and  about  .05  of  organic  nitro- 
gen. Now  we  shall  see  at  once  the 
difference  between  drinking  water  de- 
rived from  such  a  source  as  the  Thames 
and  filtered,  and  drinking  water  derived 
by  boring  into  deep  strata — into  the 
chalk.  The  chalk  water  only  contains 
.06,  that  is  the  fifth  of  the  quantity  of 
organic  carbon,  and  .01,  a  fifth  of  the 
quantity  of  organic  nitrogen  that  the 
water  supplied  by  the  Thames  Compa- 
nies contains  ;  so  that  when  you  come  to 
organic  matters,  you  see  the  difference 
at  once  between  a  water  that  is  derived 
from  a  pure  source,  and  one  from  an 


24 

impure.  The  other  method  that  I  have 
to  mention  to  you,  which  is  used  for  ex- 
pressing the  amount  of  organic  matters 
in  water,  is  called  "Wanklyn's  method/'* 
from  the  chemist  who  discovered  it. 
This  method  consists  in  the  conversion 
of  the  nitrogen  contained  in  the  organic 
matter  in  the  water,  or  a  considerable 
part  of  it,  into  ammonia,  and  then  it  is 
estimated  as  so  much  ammonia.  I  dare 
say  you  all  know  that  the  test  that 
chemists  have  for  ammonia  is  perhaps 
the  most  delicate  test  with  which  we  are 
acquainted.  This  ammonia  you  will  see 
mentioned  in  the  records  of  analysis  as 
"albuminoid  ammonia,"  and  to  a  certain 
extent  it  does  represent  the  amount  of 
organic  matter  in  the  water.  This  albu- 
minoid ammonia  in  a  drinking  water  must 
not  be  allowed  to  be  above  the  third 
place  of  decimals.  If  it  appears  higher 
than  the  third  place  of  decimals  in  parts 
of  100,000,  if  in  the  second  place,  or  if 
in  the  first,  it  is  bad.  If  in  the  first 
place  it  is  decidedly  bad  water,  and  con- 

*  See  Wanklyn's  Water  Analysis. 


25 

tains  a  considerable  amount  of  organic 
matter  in  a  state  of  solution.  You  may 
consider  that  the  albuminoid  ammonia 
represents  about  ten  times  its  weight  of 
dry  organic  matter,  and  about  forty  times 
its  weight  of  moist  organic  matter.  So 
that  .05  of  albuminoid  ammonia  in  100,- 
000  represents  about  2  parts  of  moist 
organic  matter  in  the  water.  You  see 
that,  when  you  have  an  analysis  of  water 
before  you,  you  must  consider  the  differ- 
ent things  together.  The  nitrates  help 
to  condemn  a  water  with  much  organic 
matter  in  it.  The  ammonia  does  the 
same,  and  the  chlorides  especially  so, 
and  chlorides  are  to  be  regarded  as  a 
suspicious  indication  in  water,  if  you 
have  not  good  reason  to  suppose  that 
they  come  from  some  other  source  than 
the  one  I  have  indicated.  The  danger 
of  organic  matter  in  drinking  water  con- 
sists in  this  fact  (of  course  organic  mat- 
ters are  necessary  to  us  for  our  food,  and 
it  is  not  the  mere  fact  of  its  being  organic 
matter  that  renders  it  dangerous,)  that  it 
is  organic  matter  in  a  state  of  rapid 


26 

change,  in  a  state  of  putrefactive 
change;  and  then  that  it  may  contain 
and  often  does  contain  (especially  if  it  is 
derived  from  excremental  matter)  the 
poison  of  specific  diseases,  which  may 
be  distributed  in  the  drinking  water  to  a 
population  and  cause  an  outbreak  of 
cholera,  typhoid  fever,  etc.  We  know 
now  what  sort  of  water  must  be  got  for 
drinking.  The  above  are  its  character- 
istics, and  the  water  supply  must  either 
comply  with  these  conditions,  or  be 
made  to  do  so  artificially. 

Now  how  much  of  it  is  wanted? 
You  can  look  at  this  in  two  ways.  You 
can  get  to  know  by  experience  how 
much  bodies  of  men  and  towns  always 
have  wanted.  The  amount,  of  course, 
varies  immensely  with  the  use  of  baths, 
whether  they  are  public  baths  or  not, 
with  the  amount  used  for  washing  the 
streets,  and  for  manufactures,  and  also 
with  the  amount  of  waste,  because  that 
is  a  very  important  item.  Now,  for 
washing,  drinking,  and  domestic  pur- 
poses generally,  you  may  put  it  down 


27 

(if  there  is  reasonable  amount  of  bath- 
ing) at  about  ten  gallons  a  head  a  day, 
and  then  you  must  add  nine  or  ten 
more  for  flushing  the  sewers  and  washing 
the  streets.  Much  of  this  will  be  added 
through  the  water-closets.  Thus  you 
may  say  20  gallons  a  day  without  waste 
may  be  taken  as  a  kind  of  average. 
For  trades  you  must  allow  10  gallons 
more  as  a  rule.  If  there  are  public 
baths,  and  where  there  are  many  ani- 
mals, as  horses,  which  require  about  12 
or  15  gallons  a  head  for  washing  and 
drinking,  you  must  make  a  greater  al- 
lowance. You  will  see  that  about  30 
gallons  a  head  a  day  is  the  least,  even 
where  there  is  no  extra  demand,  and 
that  is  about  the  amount  provided  in 
London,  and  that  is  about  the  least  that 
you  should  aim  at.  Professor  Kankine 
tells  you  that  35  gallons  is  the  greatest 
amount  necessary.  However,  they  don't 
think  so  everywhere.  New  York  man- 
ages to  get  through  300  gallons,  and 
does  not  find  it  too  much.  In  ancient 
Rome  (to  show  you  that  these  matters 


28 

have  been  thought  of  a  long  time  ago) 
they  had  nine  aqueducts  to  bring  water 
to  the  city.  They  thought  it  of  so  much 
importance  that  several  of  these  aque- 
ducts were  from  42  to  49  miles  long, 
and  one  of  them,  the  Marcian,  was  54 
miles  long.  Frontinus,  who  was  the 
superintendent,  and  who  wrote  a  most 
excellent  work  about  them,  giving  accu- 
rate descriptions  and  measurements  of 
them,  tells  us  the  two  most  recent  were 
made  because  the  seven  already  in  exist- 
ence "  seemed  scarcely  sufficient  for  pub- 
lic purposes  and  private  amusements." 
Now  the  sectional  area  of  the  water 
supply  to  Rome  by  these  aqueducts  was 
1,120  square  feet,  and  it  is  pretty  sure 
that  there  were  not  more  than  332,000,- 
000  gallons  daily  brought  to  Rome  by 
them.  I  suppose  there  were  not  more 
than  a  million  people  ;  that  gives  you 
about  332  gallons  a  day  that  they  found 
necessary.* 

Now,   let   me  give    you    one   or   two 

*  Mr.  James   Parker   on    the  "  Water  Supply   of 
Rome." 


29 


points  about  the  measurement  of  water 
that  you  will  find  useful.  The  measure- 
ment of  water  you  will  often  find  given 
in  cubic  meters.  A  cubic  meter  is  35J 
cubic  feet,  or  220  gallons.  T%hat  is  to 
say,  a  cubic  meter  of  water  is  220  gal- 
lons, and  as  a  ton  of  water  contains  224 
gallons,  a  cubic  meter  of  water  is  almost 
exactly  equal  to  a  ton  by  weight  (or  tun 
by  measure).  A  cubic  foot  is  rather 
more  than  6  gallons,  and  100  gallons 
are  just  about  16  cubic  feet.  Let  me 
just  give  you  an  example  of  this.  Lon- 
don, during  December,  1872,  was  sup- 
plied daily  with  100  millions,  nine  hun- 
dred thousand,  and  something  odd,  gal- 
lons of  water.  That  is  to  say  458,577 
cubic  meters,  or  about  the  same  amount 
of  tons  by  weight  or  tuns  by  measure  ; 
that  is,  201.8  gallons  to  each  house,  or 
father  less  than  a  cubic  meter  to  each 
house,  and  28.4  gallons  to  each  person. 
I  told  you  it  was  30.  Well,  it  varies  a 
little.  It  is  a  little  under  30  very  often. 
Of  the  total  amount  of  water  supplied 
to  a  place,  you  may  take  it  as  a  general  . 


30 

rule  that  80  or  82  per  cent,  is  required 
for  domestic  purpose^,  so  that  during 
that  month  of  December  in  London 
there  were  about  23£  gallons  used  for 
domestic  purposes.  Hence  the  conclu- 
sion about  the  quantity  is,  that  the 
least  you  must  endeavor  to  get  is  30 
gallons  a  head  a  day  without  any  very 
extra  demands.  Of  this  about  80  per 
cent,  \vill  be  required  for  domestic  and 
the  rest  for  public  purposes. 

So  much  for  the  quality  of  drinking 
water,  and  the  quantity  to  be  supplied. 
We  have  now  to  go  on  to  consider  the 
places  where  water  of  this  quality  and 
in  sufficient  quantity  can  be  procured. 
The  main  sources  of  water  are  rain,  and 
the  sources  that  are  subordinate  to  rain- 
fall—wells, springs,  streams  and  rivers. 
Some  other  sources  which  are  used  occa- 
sionally, and  which  are  of  very  little  use* 
for  a  great  supply,  are  such  as  the  dew, 
ice,  snow  and  distilled  water.  These 
latter  we  may  dismiss  with  a  word  or  two, 
as  only  of  exceptional  utility.  Dew  has 
,  been  used  in  deserts  and  at  sea.  Ice  and 


snow  furnish  enormous  quantities  of 
water  in  certain,,  places  where  they 
abound.  Ice  furnishes  an  exceptionally 
pure  water,  because  in  freezing  the  salts 
are  separated  out,  and  the  gases  too; 
such  water,  therefore,  requires  aeration. 
Snow  and  ice  if  used  should  not  be  col- 
lected near  to  dwellings,  because  of  the 
risk  of  contamination.  Distilled  water 
is  an  important  water  supply  now,  espe- 
cially at  sea.  Its  chief  fault  is  that  it 
requires  aeration.  To  give  it  this,  Nor- 
mandy's apparatus  may  be  used,  or  it 
may  be  allowed  to  fall  from  one  vessel 
to  another  like  a  shower.  It  has  been 
said  that  cases  of  lead  poisoning  have 
occurred  at  sea  "  partly  from  the  use  of 
minium  in  the  apparatus,  and  partly 
from  the  use  of  zinc  pipes  containing 
lead  in  their  composition."  (Dr.  Parkes.) 
'  So  much  for  the  subordinate  sources, 
which  are  all  of  little  importance  to  us. 
We  now  come  to  rain,  which  is  the 
original  source  of  all  great  supplies. 
Kain,  which  we  are  going  to  consider, 
is,  of  course,  caused  by  the  fact  that, 


32 

when  two  air  currents  come  together, 
both  saturated  with  moisture,  one  having 
a  lower  temperature  than  another,  the 
mixed  air,  though  it  has  a  mean  tempera- 
ture, has  not  the  mean  capacity  for 
water,  but  a  capacity  less  than  the  mean, 
and  so  some  of  it  falls  as  rain.  Is  rain, 
as  it  falls,  sufficiently  pure  to  be  used  as 
a  source  of  drinking  water?  In  the 
first  place  it  is  very  soft.  In  the  second 
place  it  is  well  aerated.  It  dissolves 
especially  carbonic  acid  and  oxygen  from 
the  air — the  former  being  about  three 
per  cent,  of  the  total  dissolved  gases 
and  the  latter  from  30  to  40  per  cent.  It 
contains  nitrates  and  nitrites,  especially 
during  thunder  storms.  It  contains  salts 
of  ammonia,  which  render  it  more  alka- 
line when  collected  in  the  country.  Near 
towns  it  contains  most  of  the  impurities 
that  are  found  in  the  air  of  towns,  and 
especially  it  becomes  acid  instead  of 
alkaline,  absorbing  a  large  amount  of 
the  sulphuric  acid  that  is  in  the  air.  It 
contains  organic  matter,  and  this  in  in- 
creased amount  near  towns.  Eain  half 


33 

a  mile  from  the  extreme  southwest  of 
Manchester,  although  the  wind  was 
blowing  from  the  west,  tasted  flat,  in- 
sipid, oily  and  nauseous — deposited  or- 
ganic matters,  and  even  organized  bodies 
in  considerable  quantities,  and  left  a 
clear  water  above,  containing  more  than 
two  grains  of  organic  matter  in  the  gal- 
lon. Dr.  Angus  Smith,  who  examined 
this  water,  makes  the  following  remarks : 
"  It  becomes  clear  from  the  experiments, 
that  rain-water  in  town  districts,  even  a 
few  miles  distant  from  a  town,  is  not  a 
pure  water  for  drinking ;  and  that  if  it 
could  be  got  direct  from  the  clouds  in 
large  quantities,  we  must  still  resort  to 
collecting  it  on  the  ground  in  order  to 
get  it  pure.  The  impurities  of  rain  are 
completely  removed  by  filtration  through 
the  soil ;  when  that  is  done  there  is  no 
more  nauseous  taste  of  oil  or  of  soot, 
and  it  becomes  perfectly  transparent." 
He  is  therefore  of  opinion  that  rain  col- 
lected directly  from  the  air  cannot,  at 
any  rate  near  to  towns,  afford  a  proper 
water  supply.  However,  since  rain  i$ 


34 

lie  source  of  all  the  supplies  that  we 
get,  it  becomes  necessary,  and  of  great 
importance  in  estimating  the  amount  of 
water  that  can  be  got  in  a  district,  to 
measure  the  rain-fall  of  that  district. 
Now  the  depth  of  the  rain-fall  of  a  dis- 
trict has  extraordinary  varieties,  both  as 
to  place  and  time.  For  instance,  as  re- 
gards time,  the  tropical  rain-fall  is  almost 
all  at  one  part  of  the  year.  With  us  it 
is  variable.  The  rain-fall  is  measured 
in  England  by  its  depth  in  inches.  The 
rain-fall  is  greater  in  mountainous  dis- 
tricts, and  on  the  leeward  side  of  mount- 
ains, if  they  are  not  high  enough  to 
penetrate  the  clouds;  but  if  they  are,  it 
is  on  the  windward  side,  because  the 
clouds  do  not  get  over  the  tops  of  the 
mountains.  Now,  for  the  supply  of 
water,  the  important  points  to  be  known 
about  the  rain-fall  are  these  :  The  first 
is  the  least  amount  of  rain  that  has  ever 
been  known  to  fall  in  a  year  in  a  district; 
the  minimum  annual  fall.  Then  it  is  im- 
portant to  know  the  distribution  of  the 
rain  throughout  the  year,  and  especially 


35 

the  longest  drought,  because  you  have 
got  to  provide  for  that  time  as  well  as 
for  any  other  time,  and  the  observations 
on  the  rain-fall  of  a  district  should  ex- 
tend over  not  less  than  20  years.  Of 
course  it  is  not  often  that  you  can  get 
observations  at  any  locality  that  have 
been  maintained  for  20  years,  and  so  we 
shall  have  to  consider  in  an  instant  or 
two  how  we  are  to  get  over  that  diffi- 
culty. 

The  machine  used  for  measuring  the 
depth  of  rain-fall  is  called  a  rain  gauge. 
It  is  essentially  a  funnel,  the  area  of  the 
top  of  which  is  known  very  accurately. 
The  top  of  this  funnel  is  provided  with 
a  vertical  rim  to  catch  the  splashings,  so 
that  none  may  be  lost.  Below  the  fun- 
nel there  is  a  glass  vessel  placed  to  re- 
ceive the  water.  The  height  of  the 
water  in  it  may  be  indicated  by  a  float, 
or  its  quantity  may  be  ascertained  at 
given  intervals  of  time  by  measuring  or 
weighing  it,  and  that  is  the  best  plan. 
Of  course  the  number  of  cubic  inches  of 
water,  which  is  the  same  as  the  number 


36 

of  square  inches  of  the  area  of  the  f  un- 
nel,  gives  you  one  inch  of  rain  over  that 
area.  Suppose  the  area  of  your  funnel 
is  20  square  inches,  20  cubic  inches  of 
water  will  obviously  be  the  result  of  one 
inch  of  rain- fall  over  that  20  inches.  It 
is  most  convenient  to  measure  the  water, 
and  the  measuring  glass  is  constructed  in 
the  following  way :  At  the  place  where 
that  amount  of  cubic  inches  of  water 
stands  which  is  equal  to  the  number  of 
square  inches  in  the  area  of  your  funnel 
a  line  is  drawn,  and  this  represents  one 
inch  of  rain-fall.  If  the  area  of  your  fun- 
nel is  20  square  inches,  then  you  take  20 
cubic  inches  of  water  which  you  have 
weighed  or  measured  accurately,  place  it 
in  your  glass  vessel  and  mark  one  at  the 
level  where  it  stands,  because  that 
amount  is  equal  to  a  depth  of  one  inch 
of  water  over  the  area  you  are  observing. 
One  cubic  inch  of  water  weighs  252^ 
grains,  almost  exactly.  That  one  inch  is 
divided  into  tenths  and  hundredths;  and 
with  this  vessel  you  are  able  to  measure 
the  amount  of  rain  that  has  fallen 


37 

through  the  funnel  in  a  given  time.  The 
top  of  the  gauge  must  be  placed  nearly 
level  with  the  ground ;  the  instrument 
must,  in  fact,  be  sunk.  It  must  be 
placed  in  an  open  situation,  and  a  fence 
put  around  it  if  necessary.  One  is  very 
frequently  placed  at  a  height  above  the 
ground,  and  one  on  the  ground,  to  show 
the  difference  in  the  amount  of  rain  that 
falls  at  the  two  levels.  The  amount  of 
rain  that  falls  at  the  level  of  the  ground 
(leaving  hills  out  of  the  question)  is 
always  greater  than  the  amount  that 
falls  at  any  height  above  the  ground. 
If  you  have  got  records  of  the  rain-fall 
of  a  district  for  a  considerable  number 
of  years  your  work  is  to  a  great  extent 
done,  because  then  you  have  merely  to 
take  out  the  facts  that  you  want.  If 
you  have  not,  the  only  way  to  do  it 
(with  a  limited  time)  is  to  place  rain 
gauges  at  convenient  situations,  and  as 
many  as  possible  all  over  the  district  you 
are  examining,  and  if  there  are  any  hills 
in  or  near  the  district  some  of  them 
ought  to  be  placed  on  their  tops,  and 


38 

each  of  these  rain  gauges  ought  to  be 
carefully  and  regularly  examined  at  cer- 
tain fixed  times.  Then  you  must  com- 
pare the  records  of  all  these  gauges  with 
the  results  given  by  the  nearest  rain 
gauge  that  has  been  observed  for  a  con- 
siderable number  of  years,  to  get  a  kind 
of  relation  between  the  rain  that  falls  at 
these  different  stations  on  your  district, 
and  the  rain  that  falls  at  the  nearest 
place  from  which  you  can  get  any  re- 
liable data,  and  from  this  comparison 
you  must  calculate  what  will  probably 
be  the  longest  drought  in  your  district, 
and  what  is  probably  the  least  annual 
rain-fall.  Now,  the  average  in  different 
parts  of  England  is  from  22  inches  to 
100,  or  even  120  per  annum;  in  some 
countries,  as  Burmah,  180  to  220,  and  it 
is  even  said  to  be  as  much  as  600  inches 
in  one  place.  This  useful  rule  was  given 
by  Mr.  Hawkesley  (and  certainly  the 
tables  show  that  it  is  a  very  accurate 
rule)  that  if  you  take  the  average  rain- 
fall of  a  place  for  20  years,  and  subtract 
a  sixth  from  it,  that  will  give  you 


39 

the  average  annual  rain-fall  of  the 
three  driest  years  during  that  period. 
If  you  take  the  average  annual  rain -fall 
for  20  years,  and  take  a  third  part  from 
it,  that  will  give  you  the  amount  of  rain 
in  the  driest  year  of  these  20  almost 
exactly,  and  if  you  take  the  average  of 
20  years,  and  add  a  third  to  it,  then  that 
will  give  you  pretty  nearly  the  amount 
of  rain  in  the  wettest  year. 

So  you  get  with  a  considerable  amount 
of  accuracy  the  quantity  of  rain ;  the 
least  amount  of  rain  you  are  likely  to 
get,  and  the  greatest  as  well.  Then,  of 
course,  you  want  to  know  the  area  of  the 
district,  and  besides  the  actual  amount 
of  the  rain-fall,  you  must  also  know  the 
amount  which  is  available.  In  the  first 
place,  a  great  deal  of  the  rain-fall  is  lost 
by  evaporation  and  absorption.  Evapo- 
ration from  the  surface,  and  absorption 
by  plants,  etc.  Then,  if  the  ground  is 
very  porous  to  a  great  depth,  a  consider- 
able amount  will  be  absorbed  so  fast  that 
you  cannot  collect  it.  Most  of  the  rain- 
fall is  at  once  available  from  or  near  the 


40 

surface  in  steep  countries,  and  especially 
those  which  are  formed  of  primitive  and 
metamorphic  rocks,  as  granite,  clay-slate, 
etc.,  and  generally  from  impervious 
rocks  that  are  steep-sided.  Almost  all 
the  rain-fall  in  these  cases  is  available  at 
once.  It  runs  off  the  surface  and  col- 
lects in  lakes,  and  is  available  directly. 
And  then,  on  hilly  pasture  lands  in  lime- 
stone and  sandstone  regions,  something 
like  two -thirds  of  the  rain  may  be  con- 
sidered available,  and  on  flat  pasture 
countries  something  like  one-half.  For 
instance,  on  the  green  sand,  Mr.  Prest- 
wich  estimated  that  from  36  to  60  per 
cent,  is  available.  On  chalk  and  loose 
sand  there  is  very  little  indeed  available. 
Now  one  of  the  most  important  things, 
if  not  the  most  important  thing  to  know, 
is  the  geological  character  of  the  rocks 
of  the  district  you  are  examining,  be- 
cause that  will  tell  you  a  very  great  deal 
about  the  amount  of  available  water, 
and  about  the  way  to  get  it.  We  are 
told  that  in  chalk  countries  the  rivers 
and  streams  carry  off  at  once  about  a 


41 

fifth  of  the  rain-fall ;  that  the  evapora- 
tion and  absorption  by  vegetables  and 
animals  amounts  to  as  much  as  a  third, 
and  that  the  remainder  (i.  6.,  the  greater 
part  of  the  total  rain-fall)  sinks  into  the 
ground.  In  less  absorbent  strata  you 
may  put  down  that  it  is  about  equally 
divided — that  one-third  is  carried  off  by 
the  streams,  etc.;  another  third  absorbed 
by  plants  and  animals,  or  lost  by  evapo- 
ration, while  a  third  sinks  into  the 
ground. 

Well  now,  let  us  consider  what  means 
have  been  taken  to  get  at  this  water  that 
sinks  into  the  ground.  Of  course  it  is 
got  at  by  digging  down,  and  now  we 
must  consider  in  what  strata  we  are  likely 
to  be  successful  in  digging  wells  or  mak- 
ing borings  to  get  underground  water. 
In  the  first  place,  wells  in  sands  lying 
over  impervious  strata,  over  clays  es- 
pecially, if  they  are  not  deep,  do  not,  as 
a  rule,  afford  much  water.  They  may, 
however,  afford  a  fair  supply  as  to  quan- 
tity, but  very  often  afford  a  bad  supply 
as  to  quality.  For  instance,  the  wells 


42 

sunk  into  the  sands  and  gravels  over  the 
London  clays  afford  a  very  impure  water. 
If  water  of  this  description  has  come  di- 
rectly from  the  surface,  and  especially  in 
the  neighborhood  of  towns,  it  is  contam- 
inated in  all  sorts  of  ways.  The  water 
in  these  wells  never  overflows  or  spouts 
up.  Wells,  on  the  other  hand,  sunk 
through  impervious  strata  to  pervious 
ones  below,  generally,  though  not  always, 
supply  excellent  water.  At  any  rate, 
they  have  much  greater  chance  of  sup- 
plying excellent  water,  because  they  sup- 
ply the  water  that  has  come  from  the 
high  grounds  at  a  considerable  distance. 
For  instance,  the  borings  that  are  made 
through  the  London  clay  down  to  the 
chalk,  supply  some  of  the  best  water  in 
London.  The  Kent  water  is  still  better, 
and  is  supplied  in  large  quantities  by 
borings  which  pass  through  the  chalk, 
through  the  upper  green  sand,  and 
through  the  gault  (an  inpervious  stratum) 
into  the  lower  green- sand.  These  wells 
are  known  as  Artesian  wells.  The  water 
rises  up  a  considerable  height  in  them, 


43 

and  may  overflow.  It  is  often  thought 
that  Artesian  wells  always  overflow,  but 
they  don^t.  The  water  rises  up  to  a  cer- 
tain height,  which  height  is  of  course 
determined  by  several  considerations — 
for  instance,  by  the  height  it  came  from 
originally.  Of  course  the  water  that 
you  get  from  under  Kent  is  the  water 
that  has  fallen  upon  the  outcrop  of  the 
green-sand  at  a  very  considerable  dis- 
tance round  the  London  basin. 

Mr.  Prestwich,  who  has  paid  the  great- 
est attention  to  the  water  supply  of  Lon- 
don, and  to  the  arrangement  of  the  strata 
around  London,  has  calculated  that,  from 
the  lower  green- sand  underneath  the 
London  basin,  there  is  to  be  got  an  enor- 
mous supply  of  water  for  the  metropolis, 
that  is  to  say,  on  the  presumption  that 
this  lower  green-sand  is  continuous  under- 
neath London.  It  would  not  be  fair  if  I 
did  not  tell  you  here  that  the  lower 
green-sand  does  not  appear  to  be  con- 
tinuous underneath  the  London  basin. 
Some  of  the  older  strata  are  brought  into 
contact  with  the  chalk,  so  that  the  lower 


44 

green-sand  is  missing,  probably,  under- 
neath a  great  part  of  the  district.  This 
we  know  from  deep  borings  which  have 
been  made  at  several  places.  Of  course 
the  chalk  and  also  the  green  sand  are 
merely  instances.  You  want  to  know 
the  alternation  of  the  strata  right  away 
down  the  whole  geological  series,  so  as 
to  be  able  to  say,  if  you  go  into  a  coun- 
try and  study  the  maps  and  sections  for 
a  short  time,  "  If  we  make  a  well  here 
and  bore  down,  we  shall  probably  go 
through  a  band  of  clay  into  a  pervious 
stratum,  and  get  a  supply  of  water." 
You  want  for  this  purpose  to  study  the 
geological  maps,  and  to  have  ample  time 
to  do  it.  If  we  go  below  the  chalk  into 
the  oolitic  series,  we  have  similar  alter- 
nations of  pervious  and  impervious 
strata.  When  we  go  below  this  we 
come  to  the  new  red  sandstone,  and  I 
mention  this,  because  there  is  an  im- 
portant point  connected  with  it.  The 
new  red  sandstone  is  (to  a  great  extent) 
a  pervious  stratum.  It  contains  enor- 
mous quantities  of  water,  but  the  cau- 


45 

tion  about  it  is,  that  in  many  countries 
it  holds  immense  salt  deposits.  It  is  in 
the  new  red  sandstone  of  Worcester- 
shire (for  instance)  that  the  salt  deposits 
of  Droitwich  are  found  ;  so  that  borings 
in  the  new  red  sandstone  (although  it  is 
true  that  some  towns  are  supplied  from 
that  stratum),  are  frequently  found  to 
give  a  brackish  water.  Below  this  come 
the  Permian  strata,  in  which  you  have 
the  magnesian  rocks,  that  I  mentioned 
last  time,  and  it  is  a  mischievous  thing 
to  bore  into  these  strata,  because  you 
may  get  water  containing  large  amounts 
of  magnesian  salts.  Towns  which  are 
placed  upon  these  strata  are  best  sup- 
plied (like  Manchester)  from  older  for- 
mations, such  as  mountain  limestone, 
and  so  on,  which  generally  afford  excel- 
lent water.  The  best  supplies  are  ob- 
tained from  them,  not  by  boring  or 
by  wells,  but  from  springs.  There  is 
one  thing  I  must  mention,  before  I  leave 
the  wells,  and  that  is,  that  the  sinking 
of  deep  wells  may  lower  the  level  of  the 
water  in  the  country  above  considerably, 


46 

and  that  is  a  point  that  has  often  to  be 
taken  into  consideration.  For  instance, 
Mr.  Clutterbuck  showed  that  wells  at  a 
considerable  distance  from  London  have 
been  seriously  affected  by  the  pumping 
of  the  green- sand  water  below  London. 
He  showed  that  the  level  of  the  water  in 
these  wells  was  affected  so  much,  that 
you  could  tell  by  the  levels  of  the  well 
waters  at  a  considerable  distance  from 
London,  whether  the  pumping  had  been 
going  on  in  London  on  the  previous  day 
or  not.  There  is  another  thing  that  re- 
quires to  be  known,  especially  about 
borings  in  the  chalk,  and  that  is,  that 
some  of  the  borings  will  give  an  inex- 
haustible supply  of  water,  practically 
speaking,  while  borings  close  by  will 
give  you  next  to  none.  This  Mr.  Prest- 
wich  accounts  for,  by  stating  that  the 
water  in  chalk  runs  chiefly  through 
crevices,  and  does  not  infiltrate  through 
the  mass  of  rock.  Before  I  say  a  few 
words  to  you  about  the  construction  of 
wells,  I  have  something  to  say  about 
springs,  and  the  amount  of  water  they 


47 

supply.  Now  springs  occur  where  you 
have  an  impervious  stratum  cropping 
out  from  beneath  a  pervious  one,  and 
this  may  happen  in  various  ways. 

The  water  in  springs,  and  also  that  in 
wells,  varies  very  much  in  quality  accord- 
ing to  the  place  that  it  is  taken  from. 
Spring  water  differs  from  rain  water  in 
that  it  has  passed  through  certain  rocks, 
and  dissolved  more  or  less  considerable 
quantities  of  substances  on  its  way. 
Spring  water  resembles  rain  water  in 
containing  a  considerable  amount  of  car- 
bonic acid  in  solution.  This  has  the 
property  of  dissolving  many  substances, 
one  of  the  chief  of  which  is  the  carbon- 
ate of  lime.  The  water  then  passing 
through  the  rocks  dissolves  carbonate 
and  sulphate  of  lime,  salts  of  iron,  etc. 
It  is  important  to  know  this  for  many 
reasons.  In  the  first  place,  some  of 
these  waters  dissolve,  in  mountain  lime- 
stone districts  for  instance,  so  much  car- 
bonate of  lime  as  to  become  what  is 
known  as  petrifying  springs.  Of  course 
if  you  take  a  petrifying  spring  and  bring 


48 

it  along  an  aqueduct,  under  certain  con- 
ditions your  supply  is  stopped  up ;  and 
one  of  the  aqueducts  at  Rome  is  to  be 
seen  to  this  day  perfectly  closed  for  a 
considerable  length  with  a  deposit  of 
carbonate  of  lime  and  other  salts,  be- 
cause the  contractor  took  in  a  spring 
that  he  was  not  told  to  tap — a  mineral 
spring.  Now  the  purest  spring  water 
you  can  get  comes  from  the  igneous,  the 
metamorphic,  and  the  older  stratified 
rocks.  Many  of  these  hard  rocks  yield 
a  very  pure  water  without  a  great  deal 
of  salts  in  solution.  The  mountain  lime- 
stone, the  oolitic  limestones,  and  the 
chalk  rocks  also  yield  a  good  supply, 
and  these  waters  are  fit  for  drinking  so 
long  as  they  do  not  contain  any  quantity 
of  magnesian  salts.  Water  from  sand- 
stones, especially  the  new  red  sandstone, 
I  have  told  you,  often  contains  common 
salt.  Waters  in  clay  countries  very  often 
contain  considerable  quantities  of  the 
sulphate  of  lime.  The  waters  of  the 
London  and  Oxford  clays  do,  as  also  the 
water  of  the  lower  lias  clay.  These  are 


49 

bad  waters.  They  are  permanently  bard 
and  unwholesome.  Well  waters  have 
partly  the  same  qualities,  unless  they  con- 
tain additional  impurities  from  the  causes 
I  have  mentioned  before.  River  water 
is  often  purer  than  spring  water;  that  is 
to  say,  it  often  contains  less  total  solids 
in  solution.  The  permanent  hardness  is 
generally  greater.  It  contains  less  sub- 
stances in  solution,  because  much  of  the 
carbonic  acid  has  escaped,  and  the  sub- 
stances it  held  in  solution  have  been  de- 
posited. River  water  very  often  con- 
tains much  more  organic  matter,  espe- 
cially near  towns. 

Wells  sunk  in  hard  rocks  may  require 
no  lining  at  all;  if  they  pass  through 
sandy  strata  they  require  a  lining  of 
brickwork,  and  sometimes  part  or  the 
whole  of  it  must  be  set  in  cement.  For 
an  artesian  well,  ao  ordinary  well  is  dug 
first  of  a  tolerable  breadth  and  depth, 
and  then  a  boring  is  made  which  varies 
from  twenty  down  to  three  or  four 
inches  in  depth.  As  soon  as  an  impervi- 
ous layer  is  bored  through,  and  a  pervi- 


50 

ous  stratum  reached,  the  water  rises 
through  the  boring  into  the  well  (which 
acts  as  a  sort  of  cistern),  and  has  to  be 
pumped  up,  or  it  may  rise  so  high  as  to 
overflow. 

The  ordinary  atmospheric  lifting  pump 
is  seldom  used,  but  a  kind  of  lifting  pump 
with  a  solid  piston  and  metallic  valves  is 
often  used.  In  fact,  the  cylinder  in 
which  the  solid  piston  slides  is  connected 
with  the  space  between  the  valves  above 
the  piston  instead  of  below  it.  So  that 
when  the  piston  is  raised  the  water  is 
lifted  through  the  upper  valve,  and  when 
it  is  depressed  water  is  drawn  from  the 
well  into  the  body  of  the  pump  through 
the  lower  valve.  Forcing  pumps  are 
also  used.  They  are  driven  by  engines, 
and  the  water  is  pumped  into  air  vessels, 
by  which  the  pressure  on  the  mains  is 
equalized  so  that  it  does  not  come  in 
jerks.  Let  me  mention  one  or  two  ex- 
amples of  artesian  wells,  and  the  amounts 
of  water  got  from  them  in  different 
strata.  From  the  well  of  Grenelle,  near 
Paris,  in  1860,  there  were  about  200,000 


51 

gallons  daily.  This  well  when  first  sunk 
yielded  800,000  gallons  daily,  so  that 
you  see  the  supply  has  considerably 
diminished  with  time,  which  is  an  im- 
portant thing  to  take  note  of.  The  bor- 
ing of  this  well  of  Grenelle  began  at 
twenty  inches  in  width,  and  ends  at 
about  eight  or  somewhat  less.  It  is 
1,800  feet  deep  (being  one  of  the  deepest 
borings  ever  made),  and  more  than  1,700 
feet  of  it  is  lined  with  copper  tubing, 
which  was  placed  there  instead  of  some 
wrought-iron  tubing,  with  which  it  was 
originally  lined.  The  copper  tubing  be- 
gins at  12  inches  in  diameter  and  goes 
down  to  6£.  The  temperature  of  the 
water  in  this  well  at  about  1,800  feet  is 
as  much  as  82  F.,  and  you  may  put  it 
down  that  as  a  rule,  the  temperature  of 
the  water  increases  1°  F.  for  every  50 
feet  below  the  surface.  Of  course  there 
are  certain  places  where  it  increases  very 
much  more  (about  Bath  for  instance), 
but  these  are  exceptional  cases.  The 
boring  in  the  well  at  Trafalgar  square  is 
sunk  384  feet  from  the  surface  into  the 


52 

chalk,  and  it  yields  65  cubic  feet  in  a 
minute,  or  more  than  580,000  gallons  in 
the  24  hours.  There  is  a  well  in  Wool- 
wich in  the  chalk  580  feet  deep,  which 
yields  1,400,000  gallons  in  24  hours,  and 
the  last  I  am  going  to  mention  in  the 
chalk  is  a  well  near  London — the  Am- 
well  hill  well — close  by  the  source  of  the 
New  River.  That  is  only  171  feet  deep, 
and  it  is  said  to  yield  very  nearly  2£ 
million  gallons  in  the  24  hours.*  As  all 
this  water  underneath  the  London  basin 
comes  originally  from  districts  at  some 
distance  from  London,  it  is  not  to  be 
wondered  at  that  the  pumping  at  London 
lowers  the  level  of  the  water  in  the  wells 
in  those  districts.  These  are  examples 
of  successful  borings.  Now,  a  word  with 
regard  to  the  new  red  sandstone  wells  of 
Liverpool.  These  wells  you  will  find 
described  in  the  twelfth  volume  of  the 
proceedings  of  the  Institution  of  Civil 
Engineers.  One  of  them,  called  the 
"  Bootle  Well,"  has  many  points  of  in- 
terest about  it.  Its  maximum  yield  was, 
*Hughes'  "  Water-works." 


53 

in  1853,  about  1,100,000  gallons  in  the 
24  hours.  A  curious  point  about  it  is 
that  at  the  bottom  of  the  well  instead  of 
there  being  one  boring  there  are  16  or  17. 
These  16  or  17  borings  are  of  very  differ- 
ent depths,  and  it  became  very  interest- 
ing to  know  whether  the  whole  of  them 
were  of  any  use,  and  Mr  Stephenson 
thought  of  blocking  them  up,  all  but 
one.  He  did  so,  and  found  that  one 
yielded  very  nearly  as  much  water  as  the 
16,  so  that  a  very  considerable  amount 
of  capital  had  been  wasted  in  the  boring 
of  these  holes.  That  is  worth  knowing. 
There  are  six  other  public  wells  at  Liver- 
pool in  this  new  red  sandstone,  and  the 
ordinary  yield  was  about  4£  million  gal- 
lons daily  from  them  all.  This  was  in 
Is50.  Eighteen  years  afterwards,  evi 
dence  was  given  before  the  Commission- 
ers on  the  Water  Supply  for  the  Metrop- 
olis of  a  falling  off  in  the  water  supply 
of  these  wells.  In  fact,  the  continual 
pumping  had  diminished  the  supply.  In 
1854,  these  wells  in  the  new  red  sand- 
stone at  Liverpool  were  pronounced  fail- 


54 

ures  by  Mr.  Eawlinson,  as  also  were 
others  in  England  and  America,  and  Mr. 
Piggott  Smith,  in  a  report  on  the  water 
supply  of  Birmingham,  confirmed  this, 
and  it  is  a  fact  that  they  have  had  to  be 
supplemented  by  a  supply  of  much  su- 
perior water  from  a  distance.  Mr. 
Stevenson  estimated  the  cost  of  a  pump- 
ing station  for  one  of  those  Liverpool 
wells,  including  shafts  and  steam  engines, 
at  £20,000,  and  the  annual  cost  per  mil- 
lion gallons  a  day  at  £1,324,  this  being 
without  interest  or  compensation,  but  in- 
cluding depreciation^  Generally,  well 
waters  are  liable  to  vary  in  amount  from 
month  to  month,  and  from  year  to  year, 
as  witnessed  by  the  amounts  pumped 
from  these  Liverpool  wells,  and  by  the 
amounts  pumped  year  after  year  from 
the  Cornish  mines. 

After  wells,  the  next  thing  we  have  to 
consider  is  the  way  in  which  water  can 
be  collected  from  springs  and  streams 
over  a  large  area,  called  a  drainage  area. 
That  is  one  method  of  supply,  and  the 
other  method,  of  course,  is  pumping 


55 

from  rivers.  We  tell  the  amount  of 
water  that  can  be  got  from  a  large  sur- 
face of  land,  in  the  first  place,  by  a  way 
I  spoke  to  you  about  before,  viz.:— by 
estimating  the  amount  of  available  rain- 
fall on  it.  Then  we  can  tell  it  in  another 
way,  by  correctly  measuring  the  amount 
of  water  that  is  brought  down  by 
streams  and  springs ;  so  that  we  have  to 
consider  the  methods  used  for  gauging 
springs,  streams,  etc.  The  gauge  most 
commonly  in  use  is  the  one  known  as  the 
Weir  gauge.  Weir  gauges  are  made  by 
damming  up  the  stream,  and  making  it 
all  pass  over  a  sharp  ledge  or  through 
an  orifice  or  notch,  or  row  of  notches,  on 
a  vertical  board.  Then  from  formula 
you  can,  by  means  of  tables,  calculate 
the  amount  of  water  that  passes  through 
the  notch,  or  over  the  orifice  of  the  weir 
in  a  given  time.  You  determine  the 
height  of  the  still  water  by  means  of  a 
scale,  the  zero  of  which  is  level  with  the 
base  of  the  notch,  and  you  do  it  in  this 
way.  A  stick  is  planted  in  the  bed  of 
the  stream,  its  top  at  some  little  distance 


56 

from  the  weir,  and  so  that  its  top  is  level 
with  the  base  of  the  notch,  or  row  of 
notches,  in  the  weir,  and  then  you 
measure  by  the  scale  from  the  top  of 
this  stick  to  the  level  of  the  water  from 
the  orifice.  That  is  one  way.  The  next 
plan  is  by  calculating  from  the  declivity. 
This  is  only  applicable  to  regular  chan- 
nels, like  the  New  Kiver  for  instance, 
and  if  the  stream  is  small  you  can  make 
the  whole  of  it  pass  through  a  trough, 
and  then  calculate  the  velocity  from  the 
declivity.  Another  way  is  by  measur- 
ing the  maximum  surface  velocity,  which 
is  done  by  means  o'f  floats  of  any  sort, 
or  by  means  of  fan  wheels,  and  various 
little  instruments  for  measuring  the 
surface  velocity  of  streams.  You  take 
the  maximum  surface  velocity,  and  about 
three-fourths  of  this  will  represent  the 
mean  velocity  of  the  section.  The  dis- 
charge of  springs  is  estimated  by  the 
time  taken  to  fill  a  vessel  of  known 
capacity.  A  word  about  the  permanence 
of  springs  and  streams,  which  is  an  ex- 
tremely important  point.  In  the  first 


57 

place  you  must  try  and  get  evidence 
from  maps  and  trustworthy  sources  gen- 
erally. At  the  bases  of  hills  springs  are 
usually  permanent.  In  flat  countries 
you  may  put  it  down  that  the  reverse  is 
generally  the  case.  Springs  in  limestone 
countries  are  very  permanent.  Springs 
in  very  permeable  strata  are  very  gener- 
ally variable,  unless  they  are  tapped  at 
a  considerable  distance  from  the  surface, 
and  then  they  often  give  an  enormous 
yield. 

Springs  in  primary  strata  and  in 
granite  countries  are  very  often  very 
permanent  indeed,  and  it  is  in  these 
countries  you  have  some  of  the  large 
lakes  which  are  used '  for  supplies  of 
water.  Jn  clay  basins  the  water  supply 
is  variable  as  a  rule,  being  very  great  in 
the  winter,  when  there  are  often  floods, 
and  very  small  in  summer.  In  chalk 
countries  the  springs  are  more  perma- 
nent, for  the  reason  that  they  draw  from 
considerably  beyond  the  actual  basin. 
Intermittent  springs  sometimes  occur, 
especially  in  the  chalk ;  they  are  due  to 


58 

the  gradual  collection  of  water  in  sub- 
terranean hollows,  which,  when  filled 
above  a  certain  level,  empty  themselves 
by  means  of  a  syphon- shaped  outlet ; 
it  is  obvious  that  they  must  not  be  re- 
lied on  as  sources  of  a  supply  of  water. 
This  will  end  our  consideration  of  the 
merits  of  different  localities  from  the 
water  supply  point  of  view. 

Having  found  a  sufficient  supply  of  good 
water,  or  a  sufficient  supply  of  water 
that  can  be  purified  on  a  large  scale  by 
filtration — a  subject  which  we  shall  con- 
sider further  on — or  by  means  of  Clark's 
process,  which  I  have  described  to  you, 
or  by  both  combined,  we  come  to  the 
modes  of  collection  and  distribution, 
which  vary  very  much  as  to  the  site, 
sources,  etc.  One  of  the  oldest  plans, 
and  for  all  that  one  of  the  best,  is  the 
eastern  or  Roman  plan,  if  you  like  so  to 
call  it,  which  is  that  of  tapping  natural 
springs  at  their  sources,  or  lakes,  above 
the  places  to  be  supplied,  and  conduct- 
ing the  water  by  channels  or  aqueducts 
above  or  below  ground,  or  alternately 


59 

above  and  below,  as  occasion  may  re- 
quire ;  collecting  it  in  large  cisterns,  al- 
lowing the  sediment  to  settle,  and  then 
distributing  by  means  of  gravitation. 

In  later  times  we  can  adopt  the  same 
plan,  and  distribute  either  by  gravitation 
or  by  steam  power,  as  we  choose.  Per- 
manent springs  at  a  distance  may  be  con- 
veyed by  the  Roman  plan  through  chan- 
nels across  the  country,  covered  the 
whole  way  right  up  to  the  distributing 
reservoirs  or  tanks.  The  conduits  may 
be  built  of  masonry  and  cement,  like  the 
Roman  aqueducts,  embedded  in  puddle, 
or  they  may  be  earthenware  pipes,  in 
which  case  they  must  be  laid  in  water- 
tight trenches,  and  jointed  securely,  or 
the  water  may  be  contaminated  in  vari- 
ous ways,  and  much  of  it  may  be  lost, 
or  the  pipes  may  be  of  cast  iron,  and 
this  should  be  the  case  where  deep  val- 
leys have  to  be  crossed  by  means  of  in- 
verted syphons. 

Earthenware  pipes  are  not  strong 
enough  to  be  used  as  inverted  syphons. 
The  rule  is,  that  if  the  fall  is  greater 


60 

than  1  in  300,  then  cast  iron  pipes  should 
be  used.  The  fall  of  these  conduits 
should  be  5  feet  in  a  mile,  if  they  are  of 
something  like  2  feet  in  diameter,  which 
is  of  a  small  size.  If  larger,  it  may  be 
less,  down  to  1  in  10,000,  or  6  inches  in 
the  mile.  That  is  the  fall  of  the  New 
Kiver  conduit  that  supplies  part  of  the 
north  of,  London  with  water. 

The  velocity  of  the  water  should  not 
be  less  than  one  foot  in  the  second,  so 
that  it  may  move  at  a  sufficient  rate,  nor 
greater  than  four  feet  in  a  second,  for 
fear  it  should  wear  away  the  course  by 
carrying  down  stones,  etc.  As  an  opin- 
ion about  this  plan,  which  I  am  going  to 
describe  to  you  at  greater  length,  I  may 
mention  that  Mr.  Rawlinson  stated,  in  a 
discussion  on  the  water  supply  of  Mel- 
bourne, which  you  will  find  reported  in 
Vol.  18  of  the  proceedings  of  the  Insti- 
tution of  Civil  Engineers,  that  "he 
thought  the  plan  of  gathering  spring 
water  in  Great  Britain,  by  means  of 
earthenware  pipes  to  some  common 
storage  reservoir,  was  one  that  might  be 


61 

favorably  looked  at ;  the  modern  means 
of  making  earthenware  pipes  offered 
many  facilities  ;  and  where  springs  were 
at  a  sufficient  elevation  ani  tolerably 
permanent,  the  water  might  be  collected 
and  brought  into  a  covered  reservoir  on 
the  Eastern  plan.  There  were  situations 
where  that  plan  might  be  preferable  to 
making  an  impounding  reservoir." 

Now,  I  should  like  to  give  you  a  short 
account  of  some  of  the  points  which  are 
to  be  observed  in  the  Roman  aqueducts 
at  Eome  ;  and  afterwards  I  propose  to 
give  you  an  account  of  some  extremely 
remarkable  Roman  aqueducts  which  are 
very  little  known,  and  which  have  been 
very  seldom  described,  to  wit,  the  aque- 
ducts with  which  the  town  of  Lugudu- 
num,  now  called  Lyons,  was  supplied, 
which  aqueducts  have  some  very  inter- 
esting and  instructive  points  about  them, 
as  you  will  see  directly. 

As  I  think  I  told  you  before,  Rome 
was  supplied  by  nine  aqueducts.  The 
first  two  were  built  entirely  underground 
for  their  whole  length,  because  the  water 


62 

supply  might  otherwise  have  been  cut 
off  in  case  of  invasion.  The  more  an- 
cient of  these  two,  the  oldest  of  all  the 
nine  aqueducts,  ran  for  a  distance 
of  about  11  miles.  I  need  not  say  any- 
thing more  about  that  one.  When  the 
Romans  built  the  third  aqueduct  they 
were,  it  appears,  no  longer  afraid  of  its 
being  destroyed  by  enemies,  and  so  they 
built  it  partly  above  ground,  and  partly 
underneath  the  ground.  By  the  direct 
road  to  the  place  from  which  they  took 
the  water  was  39  miles  from  Eome. 
Three  thousand  men  were  set  to  work 
at  it  under  the  Praetor  Marcius,  and  so 
it  has  been  called  the  Marcian  aqueduct. 
This  aqueduct  was  made  so  strong  that 
the  two  succeeding  ones  were  built  on 
the  top  of  it,  so  that  you  have  the 
three  channels  one  above  another.  The 
size  of  the  channel  of  the  Marcian  aque- 
duct was  about  5  Roman  feet  high  by 
2£  wide.*  The  thickness  of  each  of  the 
sides  was  a  foot.  You  can  see  this  aque- 


*  The  Koman  foot  was  equal  to  about  11. 65  English 
inches. 


63 

duct  outside  one  of  the  gates  of  Rome 
at  the  present  day. 

On  these  aqueducts  there  were  venti- 
lating shafts.  There  were  also  what  are 
known  as  piscinae,  or  small  settling  res- 
ervoirs. These  piscinae  I  shall  describe 
to  you  a  little  further  on.  Then  the 
base  of  the  channel  was  broken  up  by 
inequalities,  partly  to  help  to  break  the 
very  considerable  fall,  and  likewise  to 
aerate  the  water  by  agitation. 

I  may  now  say  a  word  or  two  about  the 
water  supply  of  the  Roman  town  of  Lug- 
udunum,  in  Gaul.  In  the  first  place,  I 
must  remind  you  that  those  aqueducts 
which  supplied  Rome  with  water  were 
carried  across  no  deep  valleys;  they  had, 
it  is  true,  often  to  be  supported  on  high 
arches,because  they  pass  over  low  ground, 
and  the  Romans  have  over  and  over  again 
been  blamed  for  not  using  syphons  ;  it 
has  been  said  that  the  Romans  were  not 
acquainted  with  the  properties  of  water, 
in  that  they  did  not  use  syphon  sin  these 
aqueducts.  We  shall  see  directly  wheth- 
er that  is  true  or  not. 


64 

The  town  of  Lugudunum  (Lyons)  was 
supplied  by  water  by  means  of  three 
aqueducts.  The  first  of  them  was  built 
in  the  first  century  before  Christ,  and 
here  is  the  description  of  it  in  a  few 
words.  It  had  two  branches,  which  unit- 
ed at  a  particular  place.  It  passed  over 
a  large  plateau  in  a  straight  line ;  then 
went  underground.  Emerging  from  be- 
neath the  ground,  it  descended,  by  means 
of  inverted  syphons,  into  a  deep  valley, 
and  was  received  at  the  bottom  of  that 
valley  on  a  supporting  bridge  of  arches. 
It  was  thus  carried  across  the  valley,  and 
ascended  the  other  side  into  a  reservoir. 
So  you  see  in  the  course  of  this  aque- 
duct, which  was  built  in  the  first  century 
before  Christ,  there  was  a  large  and 
deep  valley  crossed  by  means  of  invert- 
ed syphons,  by  the  very  method  which 
we  employ  now ;  and  this  shows  you 
that  the  Romans  then  certainly  under- 
stood and  perfectly  well  appreciated  the 
properties  of  the  syphon. 

I  will  now  give  you  a  description  of 
the  second  aqueduct  by  means  of  which 


65 

Lugudunum   was   supplied   with  water. 
It   was  underground    the  whole  way, 
and   it   carried  the   water  to   a  greater 
height  than  the  other.     The  reason  that 
it   was  constructed  at  all  was,  because 
the  water  was  required  to  be  carried  to 
a  greater  height  than  the  former  aque- 
duct brought  it.     It  was  very  nearly  the 
size  of   the  Marcian  aqueduct.     It  was 
built  of  cubical  stones  placed  together, 
as  I  may  tell  you  a  great  many  of  these 
aqueducts  were  built.     The  stones  were 
placed    together  without    cement,    and 
they  fitted  so  accurately  that  some  aque- 
ducts built  in  this  way  are  not  even  lined 
with  cement.      This   aqueduct   is  in  all 
probability  intact  at  the  present  day  for 
three-fourths   of    its   length.      Now   we 
come  to  the  third,  which  is  the  most  im- 
portant of  the  three,  and  which  is,  per- 
haps, the  most  remarkable  Roman  aque- 
duct of  which  we  have  the  remains  any- 
;  where.      The  two  former  ones  did  not 
bring   the  water   to  a  sufficient  height. 
There  is  at  Lyons  an  abrupt  hill  (Four- 
vieres),  on  which  several  Roman  palaces 


66 

were  built,  and  it  was  necessary  to  bring 
water  to  these.  The  Emperor  Claudius, 
who  was  born  at  Lugudunum,  and  who 
lived  there,  determined  to  bring  water 
onto  this  hill.  He  had  already  made  an 
aqueduct  for  Rome  (the  Claudiun  aque- 
duct), and  so  he  knew  something  about 
it.  He  had  not  used  inverted  syphons, 
however,  in  his  aqueduct  at  Rome,  and 
for  the  simple  reason,  as  you  will  pres- 
ently see,  that  it  was  practically  impos- 
sible ;  but  he  comes  and  orders  a  new 
aqueduct  to  be  built  for  the  city  of 
Lugudunum,  and  it  is  that  one  which  we 
are  now  going  to  consider,  as  briefly  as 
possible. 

This  aqueduct  descended  in  the  first 
place  into  three  or  four  valleys  on  its 
way.  The  aqueduct  was  52  kilometers 
long,  including  the  syphons.  It  had  17 
or  18  bridges  of  arches  to  carry  it  over 
low  grounds,  and  four  bridges  to  carry 
the  syphons  across  the  valleys. 

And  now  I  may  tell  you  the  size  of 
the  two  more  important  of  these  valleys. 
The  valley  of  the  river  Garon,  which  is 


67 

the  second  one  it  had  to  cross,  is  120 
meters  deep,  and  800  meters  broad. 

The  valley  of  Bonan ,  which  is 

the  next,  and  which  is  the  place  at  which 
I  examined  the  aqueduct  very  carefully 
some  time  ago ,  is  139  me- 
ters deep,  and  1,060  meters  across,  be- 
tween the  two  reservoirs,  which  are 
placed  one  on  each  side  of  the  valley. 
So  you  see  these  are  two  very  consider- 
able valleys  that  had  to  be  crossed. 

And  now,  how  did  the  Komans  man- 
age to  effect  their  purpose?  Bridges 
were  out  of  the  question,  although  we 
know  that  they  built  splendid  aqueduct 
bridges,  where  possible,  in  such  situa- 
tions, as  witness  the  well-known  Pont 
du  Gard,  near  Nismes,  which  had  three 
rows  of  arches  one  above  another,  sup- 
porting the  channel,  and  which  is  even 
now  so  perfect  that  it  is  about  to  be 
utilized  for  the  purpose  for  which  it  was 
originally  built. 

They  used  inverted  syphons.  I  told 
you  that  earthenware  pipes  will  not  do 
for  syphons.  Cast  iron  pipes  need  to 


68 

be  employed  for  large  syphons.  The 
Romans  could  only  work  iron  on  a 
small  scale,  and  so  used  leaden  syphons. 
One  thing  they  did,  and  which  it  is  im- 
portant to  note  in  this :  the  water  was 
brought  up  along  the  single  channel  of 
the  aqueduct — the  specus,  as  it  was 
called — which  in  this  particular  one  is 
about  2  Eoman  feet  broad  by  6  high, 
into  a  reservoir.  This  reservoir  had 
some  such  dimensions  as  5  yards  by 
nearly  2,  and  the  walls  were  about  a 
yard  thick ;  there  was  an  opening  in 
the  roof  for  the  purpose  of  cleansing, 
and  on  the  front  side  of  the  reservoir 
(the  one  facing  down  the  valley),  there 
were  several  holes  into  which  the  leaden 
pipes  were  fixed.  Now  one  of  these 
valleys  had  8  leaden  syphons,  another 
9,  and  another  10 ;  and  the  object,  of 
course,  of  dividing  the  water  in  this 
way  was  that  they  might  get  pipes  that 
would  resist  the  enormous  pressure,  and 
if  a  pipe  burst  the  rest  might  remain 
sound,  so  that  only  part  of  the  water 
would  be  lost.  Delorme,  I  should  tell 


69 

you,  has  calculated  that  this  single  aque- 
duct brought  11  millions  of  gallons  of 
water  into  the  place  in  24  hours.  It  is 
hardly  likely  that  it  brought  so  much  as 
that,  but  it  certainly  brought  a  consider- 
able amount. 

The  interior  of  the  channels  was  usual- 
ly constructed  of  very  small  stones  care- 
fully placed,  and  generally  laid  in  ce- 
ment. There  was  in  this  particular  one 
— and  probably  it  was  so  generally — a 
layer  of  cement  along  the  walls  of  the 
watercourse,  and  another  layer,  a  consid- 
erably thicker  one,  along  the  base  of  the 
channel.  The  arches  of  the  bridges 
were  built  of  enormous  rectangular 
blocks  of  stones,  and  the  pillars  broken 
at  certain  intervals  by  layers  of  brick- 
work buried  in  cement.  The  whole  of 
the  exterior  of  this  was  covered  over 
with  the  work  known  to  engineers  as  the 
"  opus  reticulatum,"  which  is  made  of 
cubical  pieces  of  stone,  fitted  carefully 
together. 

There  is  another  curious  thing  to  ob- 
serve, and  that  is  that  the  syphons  were 


70 

provided  with  little  tubes,  or  valves,  to 
let  out  any  air  that  might  be  carried 
down  from  the  height  by  the  water,  and 
which  might  otherwise  break  the  pipes. 
In  the  smaller  valleys  there  were  small 
leaden  tubes,  which  rose  up  from  the 
lowest  part  higher  than  the  reservoirs, 
and  in  the  larger  ones  weighted  valves 
were  used  for  the  same  purpose.  But 
what  I  want  you  to  see  in  this  is,  that 
by  the  time  the  Romans  constructed 
even  the  earliest  of  these  aqueducts  at 
Lugudunum,  they  knew  perfectly  well 
the  properties  of  water.  They  knew 
perfectly  well  they  could  make  it  travel 
up  to  the  top  of  a  hill  if  it  had  come 
down  a  slightly  higher  hill  on  the  other 
side  of  a  valley.  Now  I  just  wish  to 
give  you  the  height  of  the  reservoir  on 
the  one  side  of  the  valley  of  Bonan,  the 
deepest  of  fhem  all.  The  height  of  that 
reservoir  above  the  level  of  the  Saone  at 
Lyons,  is  151  meters,  or  something  over 
that.  At  the  other  side  of  the  valley 
into  which  the  water  was  received  the 
reservoir  was  143  meters  above  same 


71 

level,  that  is  to  say,  the  difference  in 
height  between  those  two  reservoirs  was 
only  eight  meters.  In  another  case,  it 
was  9  meters.  Not  only  then  did  they 
understand  these  matters  so  well  as  that, 
but  they  actually  lessened  this  amount 
by  causing  the  syphons  to  enter  nearest 
reservoir — the  one  nearest  the  place  to 
be  supplied — high  up  close  to  its  roof,  so 
that  they  actually  thus  diminished  the 
pressure  by  at  least  a  meter.  I  have 
given  you  this  description  at  such 
length,  because  it  shows  how  much  we 
have  to  learn  from  what  has  been  done  a 
very  long  time  before  our  own  age,  and 
also  because  there  are  so  few  descrip- 
tions of  these  splendid  aqueducts. 

We  now  come  to  the  next  plan,  that 
of  having  a  large  drainage  area,  and  of 
collecting  the  water  from  that  area  into 
an  impounding  reservoir.  Before  I  be- 
gin to  describe  this,  I  will  give  you  a 
brief  account  of  one  or  two  important 
impounding  reservoirs.  The  first  one 
will  be  that  of  the  Bivington  Pike  reser- 
voir, which  now  supplies  the  town  of 


72 

Liverpool  with  most  of  its  water.  This 
Rivington  Pike  reservoir  is  calculated  to 
supply  21  millions  of  gallons  of  water 
per  day  to  Liverpool,  and  it  has  481 
million  ^cubic  feet  of  contents,  with  a 
drainage  area  of  16^  square  miles ;  its 
embankment  is  20  feet  high.  You  will 
see  from  that,  that  it  is  calculated  to 
contain  150  days'  supply. 

Then  there  is  a  reservoir  which  was 
made  to  supply  Melbourne  with  water, 
the  particulars  of  which  are  given  in 
the  volume  from  which  I  quoted  to  you 
before,  namely,  Vol.  18  of  the  Proceed- 
ings of  the  Institution  of  Civil  Engi- 
neers, in  a  paper  by  Mr.  Bullock  Jackson. 
It  is. called  the  Yan  Yean  reservoir.  The 
description  runs  thus : 

"  The  Yan  Yean  reservoir  was  formed 
by  throwing  'an  embankment  across  a 
valley  between  two  spurs  of  hills  ;  thus 
retaining  the  rain-water  which  falls  on 
the  natural  basin,  as  well  as  the  flood- 
water  which  is  led  into  it  in  winter  from 
the  Upper  Plenty  Eiver  ;  the  river  itself 
and  the  artificial  watercourse  forming,. 


73 


in  the  latter  case,  a  vehicle  for  its  con- 
duction. The '  area  of  this  reservoir, 
when  full,  is  1,303  acres  ;  the  greatest 
depth  is  25  feet  6  inches,  and  the  aver- 
age depth  not  less  than  18  feet.  Its 
contents  measure  nearly  38,000,000  cubic 
yards,  or  upwards  of  6,400,000,000  gal- 
lons. The  area  of  the  natural  catchwater 
basin,  independent  of  the  reservoir,  is 
4,650  acres ;  so  that,  including  the  area 
of  600  acres  drained  by  the  watercourse, 
there  is  a  direct  drainage  into  the  reser- 
voir of  5,250  acres.  .  .  .  The  origi- 
nal surface  of  the  ground  at  the  site  of 
the  Yan  Yean  reservoir  consisted  of  a 
stiff  retentive  clay;  the  site  was,  there- 
fore, admirably  adapted  for  a  reservoir. 
Prior  to  the  commencement  of  the 
works,  about  two-thirds  of  the  whole 
area  were  densely  timbered  with  large 
specimens  of  eucalyptus,  which  were 
taken  up  and  burnt.  The  sides  of  the 
reservoir,  excepting  in  two  parts,  rise  in 
a  steep  slope.  The  embankment  is  1,053 
yards  in  length  at  the  top,  and  30  feet  9 
inches  in  height  at  the  deepest  part ;  the 


74 

width  at  the  top  is  20  feet ;  the  inner 
slope  is  3  to  1,  and  the  outer  slope  2  to 
1.  The  inner  slope  is  pitched  with  rough 
stones  from  15  to  20  inches  deep.  Along 
the  center  is  a  puddle  bank  and  puddle 
trench,  with  an  inner  apron  and  check 
trench.  The  puddle  trench  and  bank 
are  unusually  thick,  because,  in  the  first 
place,  almost  the  whole  of  the  material 
used  in  the  construction  of  the  bank  was 
clay,  so  that  it  entailed  little  extra  ex- 
pense ;  but  principally,  because  previous 
to  the  works  being  commenced,  the  site 
of  the  embankment  was  occupied  by 
trees  of  a  gigantic  size,  with  long  strag- 
gling roots,  which  were  all  grubbed  up, 
and  which  it  was  feared  might  leave 
clefts  in  the  soil." 

According  to  Mr.  Hawkesley,  the  con- 
siderations that  you  have  to  take  into  ac- 
count in  constructing  impounding  reser- 
voirs are  these  :  In  the  first  place  you 
have  to  consider  the  extent  of  the  drain- 
age area.  In  the  second  place,  the 
amount  of  rainfall.  And  in  the  third 
place  the  quantity  of  rainfall  which  can 


75 

be  collected  into  any  reservoir  which  it 
is  practical  to  make  in  the  district.  The 
size  of  these  reservoirs  must  be  propor- 
tioned to  the  population  to  be  supplied, 
their  area  often  requiring  to  be  -fa  of  the 
area  of  the  water- shed.  Mr.  Hawkesley 
stated  in  a  discussion,  that  he  considered 
on  an  average  of  years  that  30  inches  of 
rainfall  out  of  a  rainfall  of  48  inches, 
could  be  collected  in  an  impounding  res- 
ervoir. It  is  usually  considered  that 
one-sixth  part  of  the  total  rainfall  must 
be  put  down  as  lost  every  year  by  floods 
that  you  cannot  store.  The  water  that 
you  cannot  collect  is,  of  course,  lost  by 
evaporation  from  the  surface  of  the 
ground,  absorption  by  plants,  and  so  on. 
Now  as  to  the  site  of  the  reservoir. 
In  the  first  place  steep-sided  valleys  are 
the  best  situations.  In  the  next  place, 
it  is  necessary,  of  course,  that  the  place 
for  collecting  and  storing  water  should 
be  sufficiently  high  above  the  place  to 
be  supplied,  so  as  to  enable  you  to  sup- 
ply water  by  gravitation,  and  necessary 
also,  that  it  shall  not  be  too  high  above 


76 

it,  so  that  you  may  not  have  too  great  a 
rush  of  water. 

Then  besides  the  situation,  the  incline 
of  the  rocks  must  be  considered.  It  is 
especially  important  in  limestone  that 
the  dip  of  the  strata  shall  be  in  the 
direction  in  which  the  water  is  running, 
because  if  the  dip  is  against  it  you  very 
often  have  immense  quantities  of  water 
lost,  disappearing  between  the  strata 
and  running  away  in  another  direction. 
Stiff  impervious  clay  or  compact  rock 
affords  the  best  situation.  Trial  shafts 
or  borings  require  to  be  made  at  various 
places,  it  being  better  to  make  shafts 
than  borings,  to  see  if  .you  have  a  suffi 
ciently  impervious  material  for  the  bed 
of  the  reservoir,  and  a  sufficient  depth 
of  it.  It  is  only  with  small  reservoirs, 
as  a  rule,  that  you  can  safely  puddle  the 
whole  of  the  bottom,  or  that  it  is  done, 
and  for  this  reason  in  small  reservoirs 
the  site  is  of  less  importance,  as  you  can 
puddle  the  whole  of  the  bottom,  and 
carry  it  under  the  embankment  of  the 
puddle  wall. 


The  embankment  should  have  con- 
structed what  is  called  a  puddle  wall 
down  the  center  of  it.  I  shall  do  well 
to  give  you  some  rules  about  this.  Mr. 
Rawlinson  lays  it  down,  that  the  puddle 
wall  is  to  be  a  foot  thick  at  the  surface 
of  the  ground  for  every  three  feet  in 
height  of  the  embankment,  that  is  to 
say,  that  in  an  embankment  100  feet 
high,  the  puddle  wall  should  be  about 
33J  feet  thick  at  the  base.  Then  it 
slopes  up  to  the  top  so  as  to  be  about 
four  feet  broad  at  the  top.  Having  de- 
cided the  thickness  that  you  are  going 
to  make  the  puddle  wall  by  the  height 
that  you  are  going  to  make  the  embank- 
ment, according  to  that  rule,  you  have 
then  to  dig  what  is  called  a  puddle 
trench.  This  is  dug  down  to  a  con- 
siderable depth  into  the  impervious  bed 
that  will  be  the  bottom  of  the  reser- 
voir. The  trench  is  usually  sunk  with 
sides  sloping  towards  one  another, 
though  this  is  considered  by  some 
authorities  to  be  an  insecure  plan.  It 
would  involve  a  considerable  amount  of 


78 

extra  work,  which  would  to  a  great  ex- 
tent be  unnecessary,  to  sink  the  puddle 
trench  with  sides  diverging  from  one 
another,  as  you  would  expect  it  ought  to 
be,  and  so  it  is  sometimes  recommended 
to  sink  the  puddle  trench  with  perpen- 
dicular sides.  If  it  is  very  wet  at  the 
bottom  of  a  puddle  trench,  it  is  usual  to 
begin  filling  it  with  Portland  cement 
concrete,  and  then  to  go  on  with  the 
puddling.  For  puddling  only  the  stiffer 
kinds  of  clay  are  used.  On  each  side  of 
the  puddle  wall  a  masonry  wall  is  built, 
about  equal  to  it  in  thickness.  The  ex- 
ample I  gave  you  was  one  in  which  the 
embankment  slope  on  each  side  of  this 
puddle  wall  was  pretty  correct,  namely, 
three  to  one  inside,  and  two  to  one  out- 
side. This  embankment  is  made  of  such 
materials  as  can  be  obtained  in  the 
neighborhood,  and  the  whole  embank- 
ment must  be  made  in  very  thin  layers, 
and  should  be  trampled  in  as  much  as 
possible.  The  inner  slope  of  the  em- 
bankment is  shingled  up  to  a  little  short 
of  the  water-mark,  and  from  that  point 


79 

it  is  pitched  with  blocks  of  stones.  It  is 
sometimes  necessary  to  make  minor  em- 
bankments across  valleys  that  may  join 
with  the  one  you  are  going  to  make  into 
a  reservoir.  Now  a  reservoir  requires  a 
waste  weir  for  the  storm  waters.  This 
is  generally  made  round  the  end  of  the 
embankment,  or  cut  into  the  hillside. 
The  water  is  carried  from  this  point 
down  to  the  old  stream-course,  and  the 
channel  is  puddled  until  you  are  well 
clear  of  the  embankment. 

I  have  one  or  two  words  to  say  about 
the  reason  for  the  existence  of  these  im- 
pounding reservoirs,  and  also  about  the 
size  which  it  is  necessary  to  make  them, 
and  the  rules  that  are  laid  down  for  the 
amount  of  water  that  they  should  hold. 
In  the  first  place,  they  are  necessary 
where  a  sufficiently  copious  and  perma- 
nent supply  cannot  be  got  from  a  river 
or  large  stream,  or  from  artesian  wells, 
in  order  to  secure  a  constant  supply  of 
water  throughout  the  year,  and  they  do 
this  by  storing  the  extra  supply  of  water 
during  floods,  so  that  it  may  be  saved 


80 

for  use  in  times  of  drought ;  secondly, 
they  allow  a  settling  to  take  place  ;  and, 
in  third  place,  they  are  necessary  to  pre- 
vent damage  to  the  lower  lands  by 
floods,  for  great  damage  is  occasionally 
done  by  the  floods,  even  of  such  rivers 
as  the  Thames  and  the  Severn,  and,  of 
course,  great  quantities  of  water  are 
wasted. 

The  size  must  depend  upon  the 
amount  of  water  required,  and  upon  the 
permanence  of  the  supply ;  we  have 
reckoned  the  requisite  supply  at  thirty 
gallons  per  head  per  day.  Impounding 
reservoirs  should,  according  to  the  opin- 
ion of  many  engineers,  hold  a  six  months 
demand.  "You  can  tell  how  much  that 
is,  if  you  will  lay  down  the  amount  of 
gallons  which  you  intend  to  supply  per 
head,  and  the  population  to  be  supplied. 
If  possible,  the  gathering-ground  that 
supplies  these  reservoirs  should  be  so 
large  that  the  least  available  annual 
rainfall  is  sufficient  for  the  supply  ;  and 
then  the  reservoir  should  contain  an  ex- 
cess of  six  months  demand  over  six 


81 

months  least  possible  supply  ;  that  is  to 
say,  supposing  the  least  possible  supply 
at  any  time  during  the  year  is  zero,  then 
the  reservoir  must  contain  six  months 
demand.  The  reservoir  must  be  (to  put 
it  in  Mr.  Hawkesley's  words)  "suffi- 
ciently large  to  equalize  all  the  droughts 
and  floods  to  which  the  country  was 
subject.  Occasionally,  but  not  very  fre- 
quently, there  might  be  a  great  excess 
of  downfall,  resulting  in  floods  as  large 
as  three  or  four  hundred  times  the  mini- 
mum volume."  Now  the  minimum  vol- 
ume is  only  about  an  18th  or  20th  part 
of  the  mean  volume,  so  it  follows,  that 
the  floods  are  only  15  or  20  times  the 
mean  volume. 

Now  with  regard  to  compensation. 
It  is  necessary  in  many  instances  to 
compensate  owners,  mill- owners,  and 
others,  people  who  are  interested  in  the 
streams  that  you  are  going  to  impound, 
and,  on  an  average,  it  is  found  that  in 
England  one-third  of  the  amount  of 
water  requires  to  be  given  as  compensa- 
tion to  these  people,  and,  therefore, 


82 


two- thirds  remain  for  the  use  of  the 
town.  This  compensation,  of  course, 
must  be  considered  in  determining  the 
size  of  the  reservoir.  Sometimes  it  has 
been  arranged  that  the  amount  given  to 
the  owners  on  the  banks  should  be  the 
average  summer  discharge,  minus  the 
floods,  and  sometimes  special  compensa- 
tion reservoirs  have  been  built  to  collect 
the  water  from  a  certain  portion  of  the 
drainage  area,  these  compensation  reser- 
voirs being  entirely  under  the  control  of 
the  persons  who  are  to  be  compensated. 
However,  you  may  take  it  as  an  aver- 
age, that  about  one-third  in  England 
generally  goes  to  them. 

The  culverts  have  been  commonly 
built  through  the  embankment  in  the 
made  earth.  This  is  stated  to  be  a  bad 
plan.  Mr.  Rawlinson  says  they  should 
always  be  built  in  the  rock  or  in  the 
solid  ground,  and  not  in  the  made  earth. 
The  water  tower  is  generally  built  just 
inside  of  the  embankment,  and  the  dis- 
charge or  outlet  pipes  open  into  it  with 
valves,  which  valves  ought  to  be  inside 


83 

the  embankment,  and  not  outside  of  it. 
What  are  called  "  separating  weirs ' 
have  been  constructed  in  some  reser- 
voirs. They  are  ingenious  contrivances 
by  which  the  water,  when  at  its  ordinary 
height,  flows  over  the  weir  into  the  cul- 
vert to  be  taken  away  to  the  town. 
When  it  is  in  flood,  the  force  with  which 
it  comes  enables  it  to  pass  over  the 
opening  leading  to  the  culvert,  and  to 
get  away  into  the  old  watercourse. 
"Feeders"  for  divtrting  streams  into 
the  reservoir  are  also  sometimes  necessa- 
ry. It  is  often  found  to  be  necessary  to 
cut  a  new  course  for  the  stream  that 
runs  down  the  valley,  especially  if  it  be 
a  very  large  stream,  or  if  it  be  a  stream 
that  is  liable  to  floods. 

I  see  that  I  forgot  to  mention  one 
point,  which  I  should  have  stated  at  the 
beginning  of  the  lecture,  with  regard  to 
the  situation  of  these  reservoirs.  The  site 
must  not  be  too  low,  for  if  it  is,  the  res- 
ervoir is  necessarily  too  shallow,  and 
shallow  reservoirs  are  very  bad,  in  that 
the  water  cannot  possibly  be  kept  pure, 


84 

it  being  perfectly  impossible  to  store  it 
and  keep  it  pure  in  shallow  reservoirs. 
If  the  ground  is  too  high,  and  no  other 
suitable  place  can  be  got,  then  it  is  nec- 
essary to  make  what  are  called  "  balanc- 
ing reservoirs,"  so  that  the  force  of  the 
water  may  be  broken  by  its  being  kept 
in  a  series  of  reservoirs  at  different  levels. 

I  do  not  profess  to  have  given  you  the 
engineering  details,  as  you  will  plainly 
see.  All  I  have  tried  to  do  is  to  give 
you  some  of  the  most  important  points, 
according  to  the  best  authorities  that  I 
have  been  able  to  find. 

The  channels  are  generally  made  of 
masonry  or  brickwork.  The  water-way 
is,  according  to  Rankine,  best  semi-cir- 
cular, or  a  half  square,  or  a  half  hexa- 
gon. These  channels  are  usually  made 
cylindrical  ;  they  require  ventilating 
shafts  after  the  custom  of  the  Romans. 
Occasionally  they  are  made  with  an 
egg-shaped  section,  like  large  sewers. 

Channels  require  to  be  curved  at  their 
junctions,  or  at  any  rate  they  require  to 
be  joined  at  very  acute  angles. 


85 

With  regard  to  aqueducts,  Mr.  Kaw- 
linson  tells  us  that  "aqueducts  of  iron 
will  probably  be  cheaper  than  masonry 
or  brickwork  constructions. "  They  have 
been  made  self-supporting  by  Mr.  Simp- 
son, by  constructing  them  in  the  form 
of  tubular  iron  girders. 

Now,  with  regard  to  the  fall  of  these 
channels,  I  gave  you  one  or  two  points 
before,  when  considering  the  pipes  con- 
veying the  streams.  In  the  discussion 
on  the  water  supply  of  Paris,  in  the 
25th  Volume  of  the  Proceedings  of  the 
Institute  of  Civil  Engineers,  Mr.  Bate- 
man  gave  the  following  example  with 
reference  to  the  Loch  Katrine  aqueduct 
of  the  Glasgow  Water  Works:  "The 
fall  was  10  inches  to  the  mile  through- 
out, except  where  the  water  was  carried 
by  syphon  pipes  across  deep  valleys, 
which,  in  one  instance  of  a  hollow  of 
250  feet,  was  done  for  a  distance  of  3^ 
miles,  and  in  these  cases  there  was  a  fall 
of  5  feet  per  mile,  to  economize  the  size 
of  the  pipes." 

This  aqueduct,  I  believe,  is  about  the 


86 

largest  that  has  been  constructed.  The 
channel  is  cylindrical,  and  about  8  feet 
in  diameter.  Mr.  Rawlinson  said  in  the 
same  discussion,  that  "the  fall  of  an 
aqueduct  must  be  in  proportion  to  the 
depth  and  volume  of  water  which  it  had 
to  deliver.  The  fall  of  the  New  "River 
in  London  was  1  in  10,000,  or  6  inches 
to  the  mile,  but  with  so  large  a  volume, 
and  an  unpaved  channel,  it  was  necessary 
to  form  a  weir,  and  give  the  water  a 
vertical  fall  of  a  few  inches  at  certain 
points  of  its  course.  He  found  that 
plan  was  adopted  in  the  East.  In  laying 
out  a  line  of  aqueduct  two  principles 
were  involved.  If  it  were  graded,  as 
the  Romans  graded  some  of  theirs,  from 
5  to  15  feet  per  mile,  there  would  be 
difficulty  in  stopping  the  water  at  any 
point.  It  was  practicable,  however,  to 
grade  an  aqueduct^  having  a  fall  of  15 
feet  or  20  feet  per  mile,  if  vertical  falls 
were  introduced  at  intervals,  alternately 
with  level  or  nearly  level  lengths.  This 
mode  enabled  an  engineer  to  fix  the 
velocity,  so  as  to  prevent  undue  wash- 


87 


ing.  The  vertical  falls  tended  to  aerate 
the  water,  and  this  in  itself  constituted 
an  additional  advantage.  All  covered 
aqueduct  conduits  should  be  abundantly 
ventilated,  and  there  should  be  side  en- 
trances, stop  gates,  overflows  and  wash- 
out valves."  Sometimes  in  aqueduct 
bridges  the  sectional  area  of  the  channel 
is  diminished,  and  the  gradient  made 
steeper.  This,  of  course,  gives  greater 
velocity  to  the  water,  and  a  smaller 
amount  of  material  is  required,  and  so 
less  expense  incurred  in  constructing  the 
bridges.  So  much  as  to  the  masonry. 

Now  as  to  pipes.  Earthenware  pipes 
are  made  up  to  about  3  feet  in  diameter. 
If  they  are  of  compact  glazed  earthen- 
ware, they  are  very  tough  and  strong, 
but  they  will  not  bear  shocks,  either  the 
shocks  of  water  orv  anything  else,  and 
they  cannot  be  jointed  so  as  to  resist  a 
great  pressure,  and  so  are  not  suitable 
for  syphons.  We  will  not  say  anything 
more  about  lead  pipes,  because  they  are 
not  now  used  for  this  purpose.  Cast 
iron  pipes,  Kankine  says,  should  be  of  a 


88 

uniform  thickness;  and  he  lays  down  the 
following  rule  for  the  minimum  thick- 
ness :  "  The  thickness  of  a  cast  iron  pipe 
is  never  to  be  less  than  a  mean  propor- 
tioned between  its  internal  diameter  and 
one  forty  eighth  of  an  inch."  But,  he 
adds,  "  it  is  very  seldom  indeed  that  a 
less  thickness  than  f  of  an  inch  is  used 
for  any  pipe,  how  small  soever."  Large 
cast  iron  pipes  are  liable  to  burst,  and 
there  are  some  instances  on  record  of  it; 
one  in  the  water-works  for  the  supply 
of  Melbourne,  which  I  have  already 
mentioned  once  or  twice,  in  which  case 
the  pipe  was  33  inches  in  width,  was 
laid  through  the  embankment  of  the  res- 
ervoir and  burst.  Now  this  is  what  Mr. 
Hawkesley  said  in  a  discussion  on  the 
subject  at  the  Institution  of  Civil  En- 
gineers, about  the  bursting  of  cast  iron 
pipes :  "Cast  iron  in  the  shape  of  a 
pipe  would  stand  little  unequal  pressure 
externally,  although  such  a  pipe  would 
bear  an  enormous  pressure  when  equally 
distributed,  whether  applied  externally 
or  internally,  and  most  in  the  former 


case,  as  the  metal  then  would  be  under 
compression,"  and  he  went  on  to  say 
that,  at  u  the  Rivington  Pike  reservoir 
of  the  Liverpool  water-works,  two  lines 
of  pipes  were  carried  through  an  em- 
bankment 20  feet  high,  at  a  distance  of 
16  feet  from  the  top  of  it.  They  were 
cast  iron  pipes,  each  pipe  being  made  in 
10  or  12  pieces,  and  they  are  the  largest 
pipes  that  have  been  laid,  each  pipe 
being  44  inches  in  diameter.  Now,  out 
of  these  two  lines  of  pipes,  fully  one- 
third  of  the  pipes  so  placed,  which  were 
excellent  castings,  were  broken,  although 
they  had  borne  a  pressure  of  300  feet  in- 
ternally. The  fractures  invariably  oc- 
curred at  the  top  and  bottom,  and  not  at 
the  two  sides,  as  might  have  been  expect- 
ed. The  pipes  being  flattened  and  dis- 
torted by  the  pressdre  of  the  earth,  were 
subjected  to  a  strain  at  the  top  and  bot- 
tom greater  than  at  the  sides,  and  were 
undoubtedly  broken  by  compression. 
This  fact  convinced  him  that  pipes  in 
that  position  were  very  insecure.  Com- 
monly, in  similar  cases,  there  was  a 


90 

pressure  of  water  on  the  inside,  and  a 
pressure  of  earth  on  the  outside  ;  and  it 
was  a  usual  arrangement  for  the  valve 
which  shut  off  the  water  to  be  placed 
under  the  embankment"  (that  is  a  point 
•  I  have  referred  to  as  one  of  considerable 
importance),  "  so  that  if  a  pipe  became 
ruptured  when  in  use  the  water  would 
escape  into  the  embankment,  and  if  it 
found  its  way  to  the  back  of  the  puddle, 
the  embankment  would  be  torn  down, 
and  the  whole  of  the  water  in  the  reser- 
voir set  free.  It  was  not,  therefore,  de- 
sirable that  large  pipes  should  be  laid 
under  an  embankment,  where  they  would 
be  subject  to  a  considerable  pressure  of 
earth." 

When  a  pipe  of  that  magnitude  breaks 
it  usually  does  great  damage.  In  one  of 
these  pipes  that  I  have  just  mentioned 
to  you,  sixteen  million  gallons  of  water 
were  capable  of  being  discharged  daily, 
and  if  an  accident  occurred  there  would 
be  a  column  of  44  inches  in  diameter, 
acting  with  perhaps  200  or  300  feet  of 
pressure  to  be  dealt  with.  Another 


91 

thing  about  these  large  pipes  is,  that 
there  is  a  considerable  difficulty  in  re- 
pairing them.  One  length  of  these 
weighs  about  4  tons,  so  that  they  cannot 
easily  be  dragged  about  or  taken  up. 
Now,  cast  iron  pipes  are  said  often  to 
break  from  the  pressure  of  the  air. 
Whenever  air  gets  driven  in  along  with 
the  water,  and  especially  so  in  syphons 
where  valleys  are  crossed,  these  pipes 
are  broken  (it  is  said)  by  the  collection 
of  compressed  air. 

Mr.  Hawkesley  tells  us  that  he  con- 
siders that  they  are  broken  when  the  air 
is  let  out ;  that  it  is  the  shock  caused  by 
the  running  together  of  the  two  sepa- 
rated parts  of  the  water  that  causes  the 
breakage  of  these  pipes,  when  the  com- 
pressed air  that  is  collected  in  them  is 
let  out  too  suddenly;  and  he  recom- 
mends, and  has  practiced  in  the  case  of 
those  large  mains  at  the  Liverpool  water- 
works, the  adoption  of  valves  with  an 
aperture  of  only  f  of  an  inch ;  through 
these  the  air  rushes  out,  but  they  do  not 
permit  the  columns  of  water  to  come 


92 

together  very  suddenly ;  there  should  be 
one  of  these  at  each  place  throughout 
the  channel  where  the  pipe  is  higher 
than  the  theoretical  line,  or  than  the 
line  of  the  fall.  At  each  one  of  these 
places  air  is  liable  to  accumulate  and  to 
become  compressed,  and,  perhaps,  to 
burst  the  pipe.  At  each  one  of  these 
places,  therefore,  there  should  be  means 
of  letting  out  the  compressed  air,  and 
even  with  regard  to  this  precaution  we 
were,  as  I  showed  you  before,  forestalled 
in  the  aqueducts  of  the  ancients. 

Pipes  are  also  sometimes  burst  by  the 
pressure  of  the  water  when  a  valve  on 
the  main  is  closed ;  this  difficulty  has 
been  overcome  by  a  plan  mentioned  by 
Mr.  H.  Maudslay  at  the  Institute  of 
Civil  Engineers :  "  In  some  instances 
there  had  been  a  small  valve  and  pipe, 
so  placed  at  the  side  of  the  large  main 
as  to  join  the  main  both  before  and  be- 
yond the  large  valve,  in  order  that  the 
whole  body  of  water  might  not  act  like 
a  water-ram  on  the  closing  of  the  large 
valve.  This  plan  has  been  adopted  in 


93 

the  Neptune  fountain  at  Versailles,  and 
also,  he  believed,  in  the  mains  supplying 
the  fountains  at  the  Crystal  Palace.  On 
shutting  the  large  valve,  the  main  flow 
was  stopped,  but  the  small  pipe  permit- 
ted a  continuous  flow  of  the  smaller 
quantity,  and  thus  the  danger  of  burst- 
ing was  avoided.  The  second  valve  was 
afterwards  closed  gradually.  He  thought 
that  this  was  the  most  simple  plan  that 
could  be  adopted,  and  perhaps  the  least 
costly,  while  it  was  certainly  very  effect- 
ive." Another  plan  is  that  described  by 
Mr.  Hawkesley,  as  follows  :  "  The  valve 
upon  the  main  at  Liverpool  was  divided 
into  three  openings,  each  of  which  was 
provided  with  a  separate  screen,  so  that 
by  raising  or  lowering  each  of  these 
slowly  in  succession  the  water  was  either 
admitted  or  turned  off  very  gradually. 
The  object  of  dividing  the  valve  into 
three  apertures  was  to  enable  a  work- 
man to  operate  with  facility  on  any  one 
of  the  screws.  In  large  pipes,  where  the 
pressure  was  great,  it  was  necessary,  in 
order  that  the  brass  pieces,  upon  which 


94 

the  valve  acted,  might  not  be  abraded, 
that  only  a  certain  amount  of  pressure 
should  be  put  upon  them,  and  that  the 
friction  under  that  pressure  should  not 
be  greater  than  a  man  could  overcome, 
by  simply  turning  a  handle,  without 
stripping  the  thread  of  the  screw.  As  a 
further  provision  the  center  valve  was 
made  very  narrow  ;  the  side  valves  were 
first  closed  and  then  the  center  one,  so 
that  concussion  was  prevented.  In  ad- 
dition there  were  branches  at  various 
points,  upon  which  equilibrium  valves, 
with  a  piston  underneath,  were  placed, 
and  others  had  double  beat  valves.  But 
as  these  valves  required  to  be  heavily 
weighted,  the  inertia  of  the  weight 
-would,  if  other  means  were  not  taken, 
prevent  the  valve  from  rising  so  rapidly 
as  was  desirable.  Therefore,  between 
the  weight  and  the  valve  there  was  a 
spring,  the  action  of  which  was  inde- 
pendent either  of  the  valve  or  of  the 
weight,  so  that,  instead  of  the  valve 
waiting  for  the  large  weight  to  rise,  the 
spring  immediately  yielded  under  it  and 


95 

the  water  was  discharged  instantaneous- 
ly. When  these  valves  were  used  not 
the  slightest  shock  was  experienced.  If 
there  had  been,  the  pipe  would  undoubt- 
edly have  been  ruptured,  for  the  length 
of  the  column,  and  the  velocity,  upon 
which  the  force  of  concussion  was  de- 
pendent, were  both  very  great.  That 
was  another  reason  he  preferred  a  small- 
er pipe.  There  were  still,  however,  other 
precautions.  Powerful  disk- valves,  made 
by  Sir  W.  Armstrong  &  Co.,  and  which 
acted  in  a  similar  way  to  the  cataract 
apparatus  of  a  small  power  steam  engine 
were  placed  upon  the  main.  They  were 
made  to  close  slowly,  being  let  go  by  a 
trigger.  As  a  hundred  million  gallons 
might  pass  through  the  main  in  twenty- 
four  hours,  if  a  pipe  burst,  without  any 
provision  being  made  to  stop  the  flow,  a 
great  deal  of  mischief  would  ensue. 
Supposing,  however,  a  fracture  to  occur 
when  the  disk  valve  was  open,  then  the 
valve  would  gently  close  in  about 
two  minutes,  and  arrest  the  discharge. 
These  valves  cost  £300  each.  He  had 


96 

found  them  to  act,  on  various  occasions, 
extremely  well,  and  but  for  them  the 
country  would  have  been  flooded  on 
several  occasions." 

Now,  we  have  considered  the  Roman 
plan  and  also  the  plan  of  collecting 
water  by  drainage  areas  into  large  im- 
pounding reservoirs  and  conveying  it  by 
channels  to  the  place  that  wants  it,  the 
place  where  it  is  to  be  distributed. 
When  it  comes  there,  it  is  collected  in 
what  are  called  service  reservoirs.  The 
most  ancient  examples  of  these  service  res- 
ervoirs are  those  very  piscinae,  upon  the 
Roman  aqueducts,  which  I  have  spoken 
of,  and  you  can  see  examples  of  them  in 
Rome  at  the  present  day.  The  best  I 
ever  saw  was  at  a  place  called  Bona  in 
Algeria,  where  is  to  be  seen  a  set  of  the 
most  magnificent  service  reservoirs.  The 
plan  was  to  have  four  compartments. 
The  water  was  first  let  into  one  of  the 
two  upper  ones  ;  it  then  fell  from  that 
into  one  below,  possibly  over  a  waste- 
pipe.  The  water  then  passed,  possibly 
through  strainers,  into  another  compart- 


97 

ment  on  the  same  level,  and  it  then  rose 
through  the  roof  of  that  compart- 
ment into  a  third  at  the  level  of 
the  first  one,  out  of  which  it  went 
onwards,  and  considerable  settling 
took  place.  Now,  there  were  means 
of  scouring  out  these  two  lower 
compartments,  which  could  be  shut  off 
from  the  upper  ones  so  that  the  mud 
might  be  got  out  of  them.  The  water, 
when  it  is  brought  to  these  reservoirs  by 
either  of  these  two  methods,  or  when  it 
is  got  into  them,  as  it  very  often  is  now 
for  the  supply  of  large  towns,  directly 
out  of  the  river,  very  often  requires  to 
be  filtered,  as  mere  settling  is  not  enough 
for  it.  We  have  then  to  consider  what 
materials  are  used  for  filtering  the  water, 
what  size  the  filter  beds  require  to  be, 
and  what  effect  is  produced  on  water  by 
filtration. 

Now,  in  the  first  place,  the  materials 
that  are  commonly  used  for  filtration  are 
sand  and  gravel.  The  different  merits 
of  sand  and  gravel  and  also  of  charcoal 
I  shall  have  to  consider  in  the  next 


98 

lecture,  but  I  must  conclude  this  lecture 
by  telling  you  that  the  effect  of  filtration 
of  water,  even  by  sand  and  gravel,  is  not 
merely  the  mechanical  effect  of  remov- 
ing the  suspended  substances  that  the 
water  may  contain,  but  that,  at  the 
same  time,  there  is  a  chemical  action 
going  on.  This  is  on  account  of  the  air 
that  is  contained  between  the  little  par- 
ticles of  sand,  which  air  is  so  brought 
into  contact  with  the  finely  divided 
water  that  any  substances  in  the  water 
that  are  capable  of  oxydation  do  become 
oxydized,  and  a  considerable  amount  of 
the  organic  matters  in  the  water  are  thus 
oxydized,  and  transformed  into  innocuous 
matters.  That  is  the  first  important  point 
to  understand  about  filters,  whether  in 
filtering  water  for  drinking  purposes,  or 
with  regard  to  a  filter  about  which  we 
shall  have  to  say  more  after  a  while — a 
filter  to  purify  sewer  water. 

I  have  shown  you  that  it  was  a  fallacy 
to  suppose  that  the  Romans  did  not 
understand  the  principle  of  the  syphon, 
but  that  they  constructed  most  admir- 


99 

able  ones  on  the  aqueducts  that  brought 
water  to  Lyons.  It  so  happens,  by  a 
curious  chance,  that  I  have  recently 
seen  some  plans  and  sections  of  the 
Koman  aqueducts  which  supplied  Jeru- 
salem with  water,  and  on  one  of  those  I 
find  a  syphon,  not  made  with  lead  pipes, 
but  a  syphon  made  of  stone.  It  is  made 
of  blocks  of  stone  with  a  hole  through 
each;  the  blocks  are  put  together  so  as 
to  form  a  continuous  pipe.  Each  piece 
is  cut  at  the  end  so  that  around  the  pipe 
itself,  the  aperture  in  the  stone,  there  is 
a  ring  left  projecting  on  the  face  of  the 
stone,  and  that  ring  fits  into  a  groove  on 
the  next  stone.  That  made  a  sufficiently 
tight  syphon  to  convey  the  water,  with- 
out any  great  amount  of  leakage,  to  a 
considerable  vertical  depth  and  up  again. 
The  depth,  as  far  as  I  can  judge  from 
the  plans,  is  about  100  feet  from  the 
highest  point  to  the  lowest.  Well,  now, 
we  get  up  to  the  point  where  the  water 
has  reached  the  town,  and  there  I  told 
you  it  is  almost  necessary,  certainly 
usual,  to  construct  a  service'  reservoir. 


100 

The  Romans  constructed  them  under  the 
name  of  piscinae ;  and  I  told  you,  I 
think,  in  two  words,  how  those  were 
made ;  I  now  want  to  give  you  a  rather 
longer  account  of  their  construction. 
The  water  that  was  brought  by  one  of 
the  aqueducts  to  Rome  was  taken  direct 
from  the  river  Anio,  and  the  result  of 
taking  the  water  direct  from  the  river 
was  that  after  the  heavy  rains  it  was 
charged  with  mud,  and  though  large 
cisterns  were  provided,  in  which,  by  an 
ingenious  arrangement,  much  of  the 
sediment  was  caught,  still  it  was  not 
considered  satisfactory  by  Frontinus, 
who  was  the  engineer,  and  who,  there- 
fore, under  his  patron  the  Emperor 
Nerva,  altered  the  source.  Still  the 
water  that  came  to  Rome  required  to 
have  settling  tanks,  as  described  by  Mr. 
Parker  in  a  paper  I  quoted  before,  and 
from  which  I  again  quote : 

"  The  building  consisted  of  four  cham- 
bers— two  beneath  and  two  above.  Sup- 
posing, for  the  sake  of  illustration  and 
in  the  absence  of  a  diagram,  the  letters 


101 

,  •       ' 

represent  the  fou'r  chambers'.     The 

CD.'  v  '  "         .          '•.,•'.'.' 


channel  of  the  aq'jectoftfc;  .  ceding  "  'fr'otn". 
the  east,  at  a  tolerably  high  level  enters 
the  chamber  B.  Thence  the  water 
passed  (possibly  over  a  large  waste  pipe) 
into  the  chamber  beneath,  D.  Between 
D  and  C  there  were  communications 
through  the  wall  (possibly  provided 
with  fine  grating).  Through  the  roof 
of  C  there  was  a  hole,  and  the  water 
passed  upwards,  of  course,  finding  the 
same  level  in  A  as  in  B,  whence  it  was 
carried  off  into  another  stream.  By  the 
aid  of  sluice  gates  the  water  could  be 
transferred  direct  from  chamber  B  to 
chamber  A,  and  access  was  obtained  by 
an  opening  to  the  chambers  beneath, 
and  the  mud  was  from  time  to  time 
cleared  out." 

Just  the  same  thing  was  the  case  at 
Lugudunum  (Lyons).  Large  settling  tanks 
have  been  found  on  the  hill  of  Four- 
vieres,  consisting  of  two  reservoirs  with 
vaulted  roofs,  thus  described  :  One  of 
them  was  48  feet  long  by  44  feet  broad, 


102 

,  and  20  Test  high,  with  two  conduits  to 
^  admit  the  water,  and  several  round  holes 
-<fn  j:ht-  roof  frprh  t  which  it  could  be 
drawn.  The  walls  were  3  feet  thick, 
lined  with  very  hard  cement.  A  second 
was  100  feet  long,  12  feet  broad,  and  15 
feet  high,  divided  by  a  wall  into  two 
chambers.  A  third  was  a  large  one, 
of  which  five  of  the  supporting  arches 
remain,  and  the  discharge  conduit,  1^ 
feet  broad,  which  distributed  the  water, 
by  means  of  leaden  pipes  (of  which  a 
specimen  has  been  found)  to  the  palaces, 
gardens,  etc.  In  some  cases  similar  con- 
structions formed  public  reservoirs  from 
which  the  people  drew  the  water.  In  Rome 
"  there  were  591  open  reservoirs  (lacus) 
for  the  service  of  all  comers.  *  *  * 
These  reservoirs  were  what  we  usually 
speak  of  as  fountains ;  and  some  hun- 
dreds are  in  use  to  this  day,  many  proba- 
bly on  the  site  of  the  older  ones.  There 
were  very  stringent  laws  respecting 
their  use.  Heavy  penalties  were  inflicted 
upon  any  one  dipping  a  dirty  bucket  or 
vessel  into  the  reservoir.  There  were 


103 

also  laws  respecting  the  'overflow,'  as 
the  fountains,  of  course,  were  constantly 
running ;  these  were  the  most  important 
to  keep  in  order,  as  all  the  poorer  classes 
depended  entirely  upon  them  for  their 
supply  of  water." 

Now  let  us  consider  the  Service  Res- 
ervoirs as  they  are  made  now.  Service 
reservoirs  must  either  be  placed  at  a 
low  level,  so  that  the  water  has  to  be 
pumped  from  them,  or  high  up,  which  is 
better,  so  that  the  water,  if  not  brought 
to  them  at  that  level,  is  pumped  into 
them,  as  at  Lyons,  on  the  Rhone,  where 
the  water  is  brought  to  them  at  the 
highest  point.  They  are  made  to  con- 
tain a  few  days'  supply.  In  the  first 
place,  they  must  always  be  covered ; 
even  the  Roman  ones  were.  The  reason 
of  their  being  covered  is  that,  if  not 
covered,  the  water  becomes  impure,  for 
the  impurities  of  the  air  dissolve  in  the 
water,  and  the  growth  of  confervse  is 
also,  of  course,  very  much  aided  by 
light.  If  they  are  at  the  level  of  the 
ground,  they  are  built  of  masonry. 


104 

Mr.  Rawlinson  says,  "  The  ground  ex- 
cavated for  the  foundation  of  a  tank 
should  be  made  perfectly  water-tight. 
The  bottom  may  be  covered  with  clay 
puddle  and  the  side  walls  be  backed  or 
lined  with  clay  puddle.  The  thickness 
of  the  puddle  should  not  be  less  than  12 
inches.  If  the  site  selected  for  a  tank  is 
sand,  gravel,  or  open  jointed  rock,  great 
care  must  be  taken  to  give  the  puddle  a 
full  and  even  bearing  over  the  whole 
surface  area ;  open  joints  in  rock  must 
be  cleaned  out  and  then  filled  up  with 
concrete.  In  gravel,  large  stones  must 
be  removed  and  the  entire  surface 
brought  to  a  level,  smooth,  and  even 
plain.  Clay  puddle  will  only  resist  the 
pressure  of  water  when  it  rests  solidly 
on  an  even  bed,  so  as  to  prevent  the 
water  forcing  holes  through  it,  which 
wil]  be  the  case  if  there  is  a  rough, 
uneven  surface  and  open  space  beneath."* 

The  roof  is  supported  on  piers  with 
arches  between  the  n,  and  across  some- 

*  Suggestions  as  to  the  preparation  of  plans  as  to 
Main  Sewerage  and  Drainage  and  as  to  Water  Supply. 


105 

times  iron  columns  are  placed  in  rows 
supporting  the  girders  which  carry  the 
arches.  The  supply  pipe  has  one  or 
more  exits,  a  v  aste  and  a  wash-out, 
which  may  be  connected  by  valves  so 
that  the  supply  can  be  directly  connect- 
ed with  the  exit  independently  of  the 
tank. 

The  water  is  received  in  a  sort  of  well 
or  tower  through  which  it  passes  into 
the  tank,  and  after  settling  has  taken 
place  it  passes  out  through  a  valve  into 
the  exit  pipe.  When  the  supply  is  too 
great  it  is  carried  off  by  an  overflow  to 
which  the  wash-out  pipe  may  be  jointed. 

Well  now  I  should  like  to  give  you  a 
more  detailed  description  of  such  reser- 
voirs, and  I  take  as  an  instance,  and 
that  for  several  reasons,  the  description 
of  some  reservoirs  with  supply  tanks  : 

"The  reservoir  of  Passy  is  intended 
to  receive  the  waters  pumped  from  the 
Seine  at  Chaillot,  and  those  furnished 
by  the  Artesian  well  of  Passy  when 
disposable ;  it  is  composed  of  three  com- 
partments, two  of  which  are  covered  by 


106 

a  second  range  of  arches,  the  third,  in- 
tended as  a  reserve  in  case  of  fire,  being 
deeper  than  the  rest,  and  only  of  one 
story ;  the  two  upper  ranges  of  arches, 
also,  are  to  be  made  to  hold  a  supply  of 
water,  one-  of  them  being  covered  and 
the  other  not.  The  united  capacity  of 
these  various  compartments  is  9.227,097 
gallons,  and  their  levels  above  the  Seine 
are  respectively  arranged  at  150  feet, 
and  163  feet,  above  zero  of  the  scale  of 
the  bridge  of  la  Tournelle.  The  capacity 
of  the  separate  reservoirs  is,  for  those 
nearest  to  the  ground,  respectively 
2,232,800  and  2,344,984  gallons;  these 
are  covered  with  reservoirs  of  the  ca- 
pacity of  1,282,792  and  1,495,729  gal- 
lons ;  and  the  uncovered  side  portions 
of  the  reservoir  are  devoted  to  the  re- 
maining 870,792  gallons.  These  build- 
ings are  formed  on  the  '  tuf  du  calcaire 
lacustre,'  which  afforded  a  hard,  resist- 
ing foundation,  and  did  not  require  any 
particular  precautions  to  prevent  the 
subsidence  of  the  piers,  or  to  secure  the 
water  tightness,  or  the  impermeability 


107 

of  the  bottom.  The  external  walls  have 
been  in  consequence  carried  down  to  the 
depth  of  8  ft.  4  in.  and  have  a  width  of 
8  ft.  8  in.  all  around.  The  floors  are  of 
masonry,  1  foot  thick  in  meuliere  and 
cement,  covered  with  a  rendering  coat  of 
1£  inches  of  the  same  cement  worked  to 
a  fine  face.  This  is  covered  with  a 
range  of  cylindrical  vaults  of  10  feet 
opening,  springing  from  pillars  2  ft.  8 
in.  square  -  upon  the  top,  gradually  en- 
larging to  5  ft.  at  the  bottom.  It  is  cal- 
culated that  in  no  case  does  the  weight 
brought  upon  a  square  inch  of  this 
masonry  exceed  152  Ibs.  The  thickness 
of  the  arch  forming  the  roof  of  the  first 
tier,  and  the  floor  of  the  second  division, 
is  about  1  ft.  2  in.  on  the  crown ;  that  of 
the  roof  of  the  upper  division  is  only  4J 
inches,  executed  in  two  courses  of  tiles 
bedded  in  cement,  and  'rendered'  with  a 
coating  of  that  material  and  covered  with 
concrete. 

<l  The  reservoirs  of  Menilmontant  are 
considerably  larger  than  those  of  Passy, 
and  being  founded  upon  the  upper  mem- 


108 

bers  of  the  Paris  Basin,  special  precau- 
tions were  required  to  insure  that  the 
ground  should  not  yield  under  the  com- 
bined pressure  of  the  masonry,  and  the 
29^  million  gallons  of  water  intended  to 
be  stored.  The  marls  covering  the  gyp- 
sum of  which  the  mountain  of  Menil- 
montant  is  composed,  were  not  consid- 
ered to  be  able  to  withstand  that  weight. 
The  foundations  of  the  piers  were  there- 
fore carried  lower  down,  and  thence 
built  in  a  description  of  rough  rubble  of 
menliere  set  in  hydraulic  lime.  The 
bottom  floor  of  the  reservoir  is  arched 
over  these  piers,  and  the  upper  tier  of 
arches  rests  upon  this  floor.'' 

It  is  only  fair  to  tell  you  that  some 
engineers,  and  among  others,  Mr.  Raw- 
linson,  considered  the  plan  of  building 
two-storied  reservoirs  as  a  bad  one,  and 
not  to  be  imitated ;  but  it  is  necessary  to 
know  that  there  is  such  a  plan,  and  the 
description  applies,  to  a  great  extent,  to 
all  reservoirs. 

To  take  an  example  nearer  us,  there  is 
Mr.  Simpson's  elevated  reservoir  on  Put- 


109 

ney  Heath  ;  that  contains  ten  millions  of 
gallons  altogether.  There  is  there  a 
double  covered  reservoir  to  contain 
filtered  water  for  domestic  use,  and  a 
smaller  open  one  to  contain  unfiltered 
water  for  the  streets,  and  to  supply  the 
Serpentine,  and  so  on.  So  that  you  see 
it  is  usual  in  these  cases  to  build  several 
reservoirs  together.  This  covered  reser- 
voir that  has  to  contain  water  for  do- 
mestic purposes,  is  double,  or  constructed 
in  two  halves.  Each  part  has  an  area  of 
310  feet  by  160  feet,  and  a  depth  of  20 
feet.  The  sides  all  round  have  a  slope 
of  one  to  one.  This  gives  a  mean  area 
of  290  feet  by  140  feet,  and  a  capacity 
of  about  5,075,000  gallons  for  each  res- 
ervoir, exclusive  of  the  space  occupied 
by  the  piers.  "Hence  the  whole  ca- 
pacity may  be  taken  "  as  stated  by  Mr. 
Simpson  in  his  evidence,  "  at  10,000,000 
gallons.  The  sides  of  the  reservoir  are 
cut  out  in  the  form  of  steps,  which  are 
filled  up  with  concrete  to  a  uniform 
slope  of  one  to  one  ;  and  a  bed  of  con- 
crete one  foot  in  thickness  is  also  laid 


110 

over  the  whole  bottom  ;  each  half  of  the 
reservoir  is  covered  with  eight  brick 
arches,  averaging  rather  less  than  20 
feet  span,  the  arches  being  each  20  feet 
span,  and  the  others  18  ft.  8  in.  Two 
piers  supporting  these  arches  are  built 
lengthways,  and  are  each  310  feet  long 
at  the  top,  and  270  feet  at  the  base. 
The  arches  are  each  one  brick  in  thick- 
ness, and  are  covered  over  with  a  layer 
of  puddle,  the  haunches  being  filled  up 
with  concrete.  The  piers  are  carried 
out  14  inches  thick;  but  the  division 
wall  between  the  two  parts  of  the  reser- 
voir is  rather  more  than  four  feet  thick, 
with  a  concrete  slope  of  one  and  a  half 
to  one  on  each  side.  The  14-inch  piers 
supporting  the  arch  are  built  with  large 
circular  hollows  17  J  feet  diameter.  The 
centers  of  these  circular  hollows  are  40 
feet  apart,  so  that  solid  brickwork  23 
feet  long  is  left  between  the  circular 
hollows,  supposing  a  horizontal  section 
taken  through  the  centers  of  the  hollows. 
Each  of  the  23  feet  spaces  has  a  14-inch 
counterfort  carried  out  at  right  angles. 


Ill 

These  counterforts  occur  at  intervals  of 
26  feet  and  13  feet  alternately,  and  pro- 
ject 6  feet  wide  at  the  base,  on  each  side 
of  the  pier,  and  run  out  to  nothing  at 
the  top,  or  springing  of  the  arches." 
"  The  versed  sine  or  rise  of  the  arches  is 
5  ft.  3  in.,  or  rather  more  than  one-fifth 
of  the  span.  Each  arch  is  provided 
with  two  openings  in  the  center,  com- 
municating with  a  line  of  12  inch  earth- 
enware tubular  pipe,  which  passes 
through  the  spandrels  and  communicates 
with  perforated  iron  tops  in  the  division 
wall  between  the  two  parts  of  the  reser- 
voir. By  this  contrivance  the  space 
above  the  water  in  the  covered  reser- 
voirs is  effectually  ventilated.  The  sup- 
ply pipe  from  Thames  Ditton  is  30  in.  in 
diameter  and  comes  into  each  part  of 
the  reservoir  at  the  level  of  top  water, 
which  is  a  few  inches  below  the  spring- 
ing of  the  arches.  At  this  level  a  waste 
weir,  or  overflow,  is  fixed  to  prevent  the 
reservoir  being  filled  too  full.  The  exit 
mains  to  London  consist  of  two  24-inch 
pipes,  and  they  pass  from  the  bottom  of 


112 

the  reservoir,  which  has  an  inclination 
in  one  direction  of  1  in  20,  and  a  fall 
across  of  six  inches."  * 

Now  a  great  reason  for  the  existence 
of  these  service  reservoirs  is,  that  the 
hourly  demand  during  the  day  varies 
very  much  from  the  mean.  It  is  some- 
times so  much  as  three  times  the  mean 
demand,  during  certain  hours,  so  that  by 
this  means  it  is  not  necessary  for  the 
mains  to  be  made  inordinately  large. 
But  otherwise  the  mains  would  have  to 
be  made  large  enough  to  give  the  great- 
est demand,  instead  of  being  only  suffi- 
cient for  the  mean  demand.  And  this  is 
the  case  if  the  reservoir  is  only  large 
enough  to  contain  half  the  daily  demand. 
In  that  case  the  distributing  pipes  need 
only  to  be  calculated  to  give  the  greatest 
hourly  demand.  These  you  will  recol- 
lect are  underground  tanks.  Elevated 
tanks  are  sometimes  made  of  cast  iron, 
or  wrought  iron  plates  bolted  together, 
and  tied  by  wrought  iron  rods  at  the  bot- 
tom, to  one  another.  The  supply,  exit, 
and  overflow  pipes  ought  to  be  together 

(*Hughes'    "Waterworks.") 


113 

in  a  corner  of  the  reservoir,  in  a  small 
separate  compartment.  This  separate 
compartment  is  connected  with  the  main 
reservoir  by  a  valve,  so  that  the  main 
reservoir  can  be  cleaned  out  and  the 
supply  go  on  independently  of  it.  Thus 
you  can  shut  out  the  supply,  stop  pump- 
ing, open  a  valve,  and  let  out  all  the 
water  from  the  large  reservoir  by  the 
supply  pipe  to  the  town.  Then  you  can 
close  the  valve  and  let  the  supply  go  on 
through  this  little  separate  reservoir, 
while  the  other  is  being  mended  or 
cleaned*  out. 

The  overflow  pipe,  or  waste  pipe,  or 
whatever  you  like  to  call  it,  ought  to 
open  into  an  open  channel,  and  not  be 
connected,  as  is  very  frequently  the  case, 
with  the  nearest  drain  or  sewer.  It 
ought  to  open  above  ground,  because  as 
the  reservoir  is  covered,  if  it  does  not  do 
so,  the  foul  air  from  the  drain  will  come 
up  that  waste  pipe,  and  be  dissolved  by 
the  water  in  the  cistern,  and  so  you  will 
render  the  water  that  you  have  taken  so 
much  trouble  to  get  pure,  you  will  ren- 


114 

der  it  impure,  and  that  is  what  is  con- 
tinually done  in  all  towns,  and  in  houses, 
as  I  shall  tell  you  presently  when  speak- 
ing of  sewerage. 

For  distributing  basins  or  tanks,  Ran- 
kine  says  that  "the  most  efficient  pro- 
tection against  heat  and  frost  is  that 
given  by  a  vaulted  roof  of  masonry,  or 
brick,  covered  with  asphaltic-concrete,  to 
exclude  surface  water,  and  with  two  or 
three  feet  of  soil,  and  a  layer  of  turf.'r 
Mr.  Bawlinson  says  that  "  brick  and 
masonry  tanks,  if  arched,  may  be  cover- 
ed in  with  sand,  or  fine  earth,  to  the 
depth  of  18  inches,  which  will  preserve 
the  water  cool." 

Up  to  the  present  time  we  have  been 
describing  works  connected  with  im- 
pounding reservoirs  ;  now,  with  regard 
to  river  works.  With  river  works  you 
still  more  certainly  require  settling  res- 
ervoirs into  which  water  may  either  flow 
directly  through  culverts  from  the  river, 
as  it  does  at  Chelsea,  or  into  which  it 
may  be  pumped.  When  the  water  flows 
in  from  culverts,  you  require  almost  in- 


115 

variably  to  have  filter  beds,  which  we 
shall  describe  a  little  further  on.  Some- 
times for  river  works  it  is  necessary  to 
construct  a  weir  right  across  the  river, 
in  order  to  keep  the  water  as  near  as 
may  be  at  constant  level.  The  engine 
power  employed  ought  to  be  consider- 
ably greater  than  that  which  is  actually 
wanted,  one-third  greater  at  any  rate, 
and,  of  course,  there  ought  always  to  be 
a  reserve  engine.  At  the  Chelsea  works, 
to  which  I  have  before  referred,  the  de- 
positing reservoirs  are  made  in  London 
clay,  and  the  bottom  and  sides  are  mere- 
ly lined  with  cement  placed  upon  this 
clay.  From  this  the  water  passes  direct 
to  the  filter  beds. 

With  regard  to  those  cases  in  which 
the  water  is  taken  from  rivers,  there  are 
certain  things  I  want  to  tell  you.  I 
want  to  tell  you  something  about  the 
purification  of  river  water.  We  know 
that  into  rivers,  especially  in  thickly 
populated  countries,  an  enormous 
amount  of  refuse  matter  of  all  sorts  is 
thrown,  and  it  is  necessary  to  know 


116 

whether  this  refuse  matter  is  destroyed 
in  its  passage  along  the  rivers,  that  is 
to  say,  whether  the  water,  after  running  a 
certain  distance,  becomes  sufficiently  pure 
to  be  used  for  drinking.  And  now  I 
must  quote  to  you  from  a  book  from 
which  I  shall  have  occasion  to  quote  a 
great  many  times  during  the  course  of 
the  remaining  lectures,  a  book  entitled 
"A  Digest  of  Facts  relating  to  the 
Treatment  and  Utilization  of  Sewage." 

"  The  evidence  collected  on  this  head 
by  the  Koyal  Commission  on  Water 
Supply  was  very  various.  Dr.  Frank- 
land  says: 

c  There  is  no  process  practicable  on  a 
large  scale  by  which  that  noxious  mate- 
rial (sewage  matter)  can  be  removed 
from  water  once  so  contaminated,  and 
therefore  I  am  of  opinion  that  water 
which  has  been  once  contaminated  by 
sewage  or  manure  matter  is  henceforth 
unsuitable  for  domestic  use.'  " 

Now  the  results  of  experiments  are 
found  to  give  the  following  facts  : — In 
the  first  place  it  appears  that  in  rivers 


117 

that  are  well  known  to  be  polluted,  and 
the  water  of  which  has  a  temperature 
not  exceeding  64°  Fahrenheit,  a  flow  of 
between  eleven  and  thirteen  miles  "  pro- 
duces but  little  effect  upon  the  organic 
matter  dissolved  in  the  water."  To  re- 
move all  uncertainty  from  the  "  varia- 
bility of  the  composition  of  the  river 
waters  at  different  times  of  the  day,"  ex- 
periments were  made  by  mixing  filtered 
London  sewage  with  water  ;  6i  it  was 
then  well  agitated  and  freely  exposed  to 
the  air  and  light  every  day,  by  being 
syphoned  in  a  slender  stream  from  one 
vessel  to  another,  '  falling  each  time 
through  three  feet  of  air."  The  mixture 
which  originally  contained  in  100,000 
parts  .267  of  organic  carbon  and  .081  of 
organic  nitrogen  was  found  to  contain, 
after  96  hours,  .250  of  organic  carbon 
and  .058  of  organic  nitrogen ;  and  after 
192  hours,  .2  of  organic  carbon  and 
.054  of  organic  nitrogen.  The  tempera- 
ture of  the  air  during  this  experiment 
was  about  20  deg.  Cent.  (68°  Fahrenheit). 
"These  results  indicate  approximately 


118 

the  effect  which  would  be  produced  by 
the  flow  of  a  stream  containing  10  per 
cent,  of  sewage  for  96  and  192  miles 
respectively,  at  the  rate  of  one  mile  per 
hour."  They  show,  then,  that  at  the 
above  temperature,  during  a  flow  of  96 
miles,  at  the  rate  of  one  mile  an  hour, 
the  amount  of  organic  carbon  was  re- 
duced 6.4  per  cent.,  that  of  organic 
nitrogen  28. 4  per  cent.;  while  during  the 
flow  of  192  miles,  at  the  same  rate, 
the  amounts  of  these  two  substances 
were  only  reduced  25.1  and  83.3  percent, 
respectively.  It  is  shown  that  the  oxy- 
dation  of  this  organic  matter  is  chiefly 
affected  by  the  amount  of  atmospheric 
oxygen  dissolved  in  the  water,  "such 
dissolved  oxygen  being  well  known  to 
be  chemically  much  more  active  than  the 
gaseous  oxygen  of  the  air." 

It  was  found,  however,  that  the  action 
of  this  dissolved  oxygen  was  not  really 
anything  like  so  quick  or  so  perfect  as 
generally  supposed,  and  that  62  per  cent, 
of  the  sewage  was  the  maximum  quan- 
tity that  would  be  oxydized  during  168 


119 

hours,  even  supposing  that  the  oxydation 
took  place  during  the  whole  time  at  the 
maximum  rate  observed,  which  was  cer- 
tainly not  the  case. 

£;  "  It  is  thus  evident,  that  so   for  from 
sewage  mixed  with  20  times  its  volume 
of  water  being  oxydized  during   a   flow 
of  10  or  12  miles,  scarcely  two-thirds  of 
it  would  be  so  destroyed  in  a  flow  of  168 
miles  at  the  rate  of  one  mile  per  hour,  or 
after  the  lapse  of  a   week.     .     .     .     .     . 

Thus,  whether  we  examine  the  organic 
pollution  of  a  river  at  different  points  of 
its  flow,  or  the  rate  of  disappearance  of 
the  organic  matter  of  sewage  when  the 
latter  is  mixed  with  fresh  water  and 
violently  agitated  in  contact  with  air,  or 
finally  the  rate  at  which  dissolved  oxygen 
disappears  in  water  polluted  with  5  per 
cent,  of  sewage,  we  are  led  in  each  case 
to  the  inevitable  conclusion  that  the 
oxydation  of  the  organic  matter  in  sew- 
age proceeds  with  extreme  slowness, 
even  when  the  sewage  is  mixed  with  a 
large  volume  of  unpolluted  water,  and 
that  it  is  impossible  to  say  how  far  such 


120 

water  must  flow  before  the  sewage  mat- 
ter becomes  thoroughly  oxydized.  It 
will  be  safe  to  infer,  however,  from  the 
above  results,  that  there  is  no  river  in 
the  United  Kingdom  long  enough  to  ef- 
fect the  destruction  of  sewage  by  oxy- 
dation. 

Now  there  were  several  scientific  men 
who  gave  evidence  of  another  sort,  and 
who  declared  that  practically  speaking 
water  was  sufficiently  pure  after  even  a 
short  flow.  The  answer  to  that  state- 
ment is  found  if  we  just  go  into  a  few 
of  the  public  health  facts.  Here  is  one. 
This  is  gathered  from  Mr.  Simon's  re- 
port on  the  cholera  epidemics  of  London 
in  1848-49  and  1853-54.  "When  the 
Lambeth  Company  took  its  water  from 
the  Thames  near  Hungerford  Bridge, 
the  people  who  drank  that  water  died  at 
the  rate  of  12.5  per  thousand.  When 
the  source  of  supply  was  moved  to  the 
Thames  at  Thames  Ditton,  the  mortality 
was  only  3.7  per  thousand,  while  at  the 
same  time,  and  in  the  same  districts,  the 
mortality  among  the  people  who  were 


121 

supplied  with  water  by  the  Southwark 
Company  from  the  Thames  at  Battersea 
was  at  the  rate  of  13  per  thousand." 

I  could  give  you  any  number  of  facts 
of  that  sort  to  show  you  that  water  that 
has  been  polluted  is  dangerous  to  drink. 
I  may  just  mention  to  you  the  opinion 
which  Sir  Benjamin  Brodie,  the  late  Pro- 
fessor of  Chemistry  at  Oxford,  has 
given ;  he  said  in  his  evidence  before 
the  Kivers'  Pollution  Commissioners  : — 
"I  believe  that  an  infimtesiinally  small 
quantity  of  decayed  matter  is  able  to 
produce  an  injurious  effect  upon  health. 
Therefore  if  a  large  proportion  of  or- 
ganic matter  was  removed  by  the  pro- 
cess of  oxydation  the  quantity  left 
might  be  quite  sufficient  to  be  inj  urious 
to  health.  With  regard  to  the  oxyda- 
tion we  know  that  to  destroy  organic 
matter  the  most  powerful  oxydizing 
agents  are  required;  we  must  boil  it 
with  nitric  acid  and  chloric  acid,  and  the 
most  perfect  chemical  agents.  To  think 
to  get  rid  of  organic  matter  by  exposure 
to  the  air  for  a  short  time  is  absurd." 


122 

I  give  you  those  statements  in  order 
to  bring  you  to  the  conclusion  to  which 
I  wish  you  to  come,  namely,  that  we 
should  not  take  water  for  the  supply  of 
villages  and  towns  from  a  river  that  has 
been  contaminated  at  all,  if  it  can  pos- 
sibly be  helped ;  that  it  has  never  been 
proved  that  such  water  gets  really  pure 
again ;  and  that  at  certain  times  there- 
fore very  considerable  danger  may  arise 
from  drinking  such  water ;  in  fact,  as 
Mr.  Simon  said  when  examined  before 
the  Koyal  Commission  on  Water  Supply, 
"it  ought  to  be  made  an  absolute  con- 
dition for  a  public  water  supply  that 
it  should  be  uncontaminable  by  drain- 
age." 

The  water  when  taken  from  the  river, 
or  even  if  it  is  taken  from  the  gentle 
slopes  of  cultivated  lands,  and  also  in 
some  other  instances,  requires  to  be  fil- 
tered as  well  as  allowed  to  settle  ;  de- 
position is  not  sufficient  of  itself.  It  is 
important,  also,  to  keep  out  inferior 
waters,  that  is  when  there  are  several 
sources  ;  and  with  this  condition  you 


123 

may  prevent  the  necessity   of   the  water 
all  requiring  to  be  filtered. 

Mr.  Parker  says:— "At  last  it  may  be 
interesting  to  know  what  Frontinus  did, 
or  rather,  what  he  says  with  becoming 
modesty,  his  patron,  the  Emperor  Nerva, 
accomplished  on  this  score  :  '  But  the 
water  of  the  Anio  Novus  often  spoilt  the 
rest,  for  since  it  was  the  highest*  as  to 
level,  and  held  the  first  rank  as  to  abund- 
ance, it  was  most  often  made  use  of  to 
help  the  others  when  they  failed.  The 
stupidity,  however,  of  the  Aquarii  was 
such  that  they  had  introduced  this 
water  into  the  channels  of  several  others 
where  there  was  no  need,  and  spoilt 
water  which  was  flowing  in  abundance 
without  it.  This  was  the  case  especially 
as  regards  the  Claudian,  which  came  all 
the  way  for  many  miles  in  it6  own  chan- 
nel perfectly  pure,  but  when  it  reached 
Borne  and  was  mixed  with  the  Anio  it 
lost  all  its  purity.  And  thus  it  happen- 
ed that  many  were  not  in  fact  helped  at 
all  by  the  addition  of  the  extra  water, 
through  the  want  of  care  on  the  part  of 


124 

those  who  distributed  it.  For  instance, 
we  found  even  the  Marcian,  the  most 
pleasant  to  drink  on  account  of  its 
brightness  and  freshness,  in  use  in  the 
baths,  and  by  the  cloth-fullers,  and  ac- 
cording to  all  accounts  employed  for  the 
most  base  services.  It  pleased,  there- 
fore, the  Emperor  to  have  all  these  sepa- 
rated, and  for  each  to  be  s,o  arranged 
that  first  of  all  the  Marcian  should  be 
assigned  to  its  own  use,  so  that  the  Anio 
Vetus,  which  from  various  reasons  was 
found  to  be  less  wholesome,  as  well  as 
being  at  a  low  level,  should  be  employed 
for  the  watering  of  the  gardens  in  the 
suburbs,  and  in  the  city  itself,  for  viler 
purposes.'" 

So  you  see  they  had,  even  then,  found 
out  that  one  water  was  more  wholesome 
than  another,  and  when  they  had  got 
supplies  from  two  or  three  sources  they 
knew  it  was  better  to  keep  them  sepa- 
rate, and  so  use  the  best  one  for  drink- 
ing purposes  and  the  inferior  ones  for 
other  purposes. 

Now  when  water  containing  substances 


125 

in  suspension  is  passed  through  a  medium 
provided  with  fine  pores,  it  is,  of  course, 
at  least  the  purer  by  virtue  of  the  re- 
moval of  all  such  matters  as  are  unable 
to  pass  through  the  pores.  If  that  were 
all  that  filtration  accomplished,  it  would 
be  only  a  fine  straining  process.  But 
that  is  not  all.  If  you  take  a  large 
quantity  of  porous  material,  for  instance, 
a  large  mass  of  sand,  or  gravel,  or  espe- 
cially charcoal — almost  any  porous  ma- 
terial— and  pass  water  through  it,  water 
containing  certain  substances  in  solution, 
and  certain  substances  in  suspension, 
those  in  suspension  will  remain  unless 
they  are  fine  enough  to  pass  through  the 
pores  of  the  material.  But  all  these 
porous  substances  contain  an  immense 
amount  of  air  between  their  pores,  and 
the  water  ^y  being  passed  through  them 
is  divided  into  an  infinite  number  of  ex- 
ceedingly small  rivulets,  exceedingly 
small  streams,  and  so  the  substances  in 
solution  in  the  water  are  brought  into 
the  closest  possible  contact  with  the 
oxygen  of  the  air  between  the  pores  of 


126 

the  filtering  material,  and  so  when  you 
have  passed  the  water  through  a  filter, 
a  chemical  action  takes  place,  and  not 
merely  a  mechanical  action.  You  have 
a  mechanical  action  first,  and  then  you 
have  also  a  chemical  action.  That  chemi- 
cal action  consists  in  the  oxydation  of 
the  substances  held  in  solution  in  the 
water — that  is,  such  substances  as  are 
capable  of  oxydation,  and  these  are  the 
ammonia  and  the  putrescible  organic 
matters  which  are  so  dangerous  when 
left  in  drinking  waters. 

One  of  the  best  filtering  substances, 
that  is,  one  which  alters  the  substances 
contained  in  water  most  in  its  passage 
through  it,  is  animal  charcoal,  and  you 
will  find  in  the  26th  and  27th  vols.  of 
the  Proceedings  of  the  Institution  of 
Civil  Engineers,  a  most  important  and 
interesting  discussion  on  this  property  of 
animal  charcoal,  and  other  substances — 
sand,  and  so  on — upon  the  power  of 
these  materials  to  cause  the  oxydation 
of  substances  in  water.  I  should  tell 
you  that  the  paper  itself  to  which  I  re- 


127 

fer  in  that  26th  vol.  is  not  worth  read- 
ing, but  the  discussion  afterwards  is  very 
well  worth  careful  study.  The  paper  is 
worthless,  because  it  came  to  an  entirely 
erroneous  conclusion  on  account  of  the 
experiments  being  performed  by  a  pro- 
cess which  is  practically  worthless. 

Here  I  must  give  you  an  example. 
Dr.  Frankland  tells  us  that  he  filtered 
New  River  water  through  animal  char- 
coal; that  before  filtration  it  contained 
in  solution  about  18  grains  in  a  gallon  of 
solid  matters,  that  after  filtration  it  con- 
tained 11.6.  Of  course  you  are  pre- 
pared for  a  less  amount  of  impurity  after 
filtration.  Now  the  organic  and  other 
volatile  matters  contained  in  the  water 
before  filtration  amounted  to  .37  of  a 
grain  in  a  gallon,  and  after  filtration  the 
amount  was  15 ;  that  is  to  say  that  more 
than  one-half  of  these  matters  were  re- 
moved by  filtration  through  animal  char- 
coal. After  a  month  this  charcoal  re- 
moved still  more  organic  matter,  and 
some  mineral  matters  as  well,  and  even 
a  few  months  afterwards  one-half  of  the 


128 

organic  and  volatile  matters  'only  re- 
mained after  filtration.  These  experi- 
ments show  a  very  important  thing, 
which  is  perfectly  true  of  a  sand  filter 
as  it  is  of  an  animal  charcoal  filter,  and 
that  is,  it  is  not  by  storing  up  these  mat- 
ters that  a  filter  works,  or  else  it  would 
be  of  no  use  whatever  to  make  a  filter. 
You  would  have  it  choked  up  in  a  very 
short  time,  and  it  would  continually  have 
to  be  renewed,  whether  made  of  sand,  of 
gravel,  of  charcoal,  or  what  not.  It  is 
by  oxydizing  the  substances  that  the 
advantage  is  obtained,  and  the  results  of 
oxydation  you  can  find  in  the  water 
afterwards,  and  these  results  of  the  oxy- 
dation are  nitrates  and  nitrites,  and  car- 
bonates. Of  course  these  are  harmless 
matters,  and  that  is  the  important  action 
which  a  filter  has.  Dr.  Frankland  stated 
that  he  had  passed  the  water  supplied  to 
London  by  the  Grand  Junction  Company 
through  a  thickness  of  three  feet  of  ani- 
mal charcoal,  at  the  rate  of  41,000  gal- 
lons per  square  foot  per  day  of  twenty- 
four  hours,  under  a  head  of  water  of 


129 

thirty  feet,  the  charcoal  being  in  granules 
like  coarse  sand,  and  that  at  that  rate — 
a  tremendous  rate — more  than  one-half 
of  the  organic  matter  was  removed. 
He  thought  from  these  experiments  on 
animal  charcoal  that  persons  who  had  to 
supply  water  to  towns  ought  to  use  it,  as 
at  any  rate  one  of  the  media  in  the  filter 
beds.  I  must  not  pass  from  charcoal 
without  mentioning  that  vegetable  char- 
coal is  agreed  on  nearly  all  hands  to  be 
almost  entirely  useless  for  purposes  of 
filtration.  In  the  first  place  it  contains 
enormous  amounts  of  salts  which  are 
soluble  in  water,  so  that  the  water  be- 
comes very  much  harder  in  passing 
through  it  than  before,  and  then  it  does 
not  purify  water  in  the  way  that  animal 
charcoal  does. 

Well,  now  some  of  the  effects  of  sand 
filters,  as  employed  by  the  Water  Com- 
panies, Wanklyn  points  out.  He  says- 
that  the  Thames  water  at  Hampton  con- 
tains fifteen  parts  of  albuminoid  am- 
monia, or  ammonia  derivable  from  or- 
ganic matter,  in  one  hundred  millions, 


130 

that  is  to  say,  .15  in  100,000,  which  is  the 
way  we  have  generally  reckoned  it,  and 
that  after  filtration  by  the  company  it 
only  contains  5  or  6;  so  that  you  see 
water  is  capable  of  being  purified — that 
is,  the  matters  in  solution  are  capable  of 
being  altered  in  drinking  water  on  an 
immense  scale. 

Now  what  sort  of  things  are  these 
filter  beds,  as  they  are  made?  because 
laboratory  experiments  are  all  very  well, 
but  you  have  practically  to  do  it  on  a 
large  scale.  Mr.  Hawkesley  has  made 
some  large  water- works,  as  you  are  most 
of  you  probably  aware,  at  Leicester,  and 
there,  there  is  a  reservoir  of  forty  acres 
in  extent.  There  are  also  four  filter 
beds,  each  ninety  nine  feet  long,  and 
sixty-six  feet  wide,  and  eight  feet  eight 
inches  deep  from  the  ground.  The  water 
comes  in  separate  channels  to  these  filter 
beds,  and  it  is  passed  downwards  through 
the  following  filtering  materials: — Two 
feet  six  inches  of  sand,  and  then  two 
feet  six  inches  of  layers  of  gravel  of 
various  sizes  (from  the  size  of  beans  up 


131 

to  eggs)  to  the  drains  below,  and  thence 
by  pipes  into  an  octagonal  pure  water 
tank.  This  tank,  eight  feet  eight  inches 
deep,  holds  seven  feet  eight  inches  of 
water,  and  is  sixty- six  feet  from  side  to 
side.  That  is  the  general  plan. 

The  supply  comes  to  the  filter  beds 
from  the  reservoir  at  various  points  ;  it 
passes  through  two  feet  six  inches  of 
coarse  sand — for,  it  must  be  observed, 
fine  sand  will  not  do,  as  it  gets  choked 
up  by  the  suspended  matters  in  the 
water — and  then  through  two  feet  six 
inches  of  gravel.  The  filtering  beds 
have  sloping  sides  and  are  made  of  sand, 
fine  gravel,  coarse  gravel,  then  very 
coarse  gravel,  with  a  drain  at  the  bot- 
tom. The  filtered  water  is  delivered 
into  an  upright  pipe  in  the  tank,  which 
comes  within  two  feet  of  the  top,  so 
that  the  pressure  of  the  water  on  the 
beds  from  above  can  never  be  greater 
than  that  due  to  a  height  of  two  feet. 
It  is  essential  that  the  pressure  on  the 
surface  of  the  beds  should  not  be  too 
great. 


132 

Well  now  from  these  filters  six  hun- 
dred or  seven  hundred  gallons  per  day 
per  square  yard  flow,  and  the  proper 
rate  of  vertical  descent  for  the  water,  as 
it  is  generally  considered,  is  six  inches 
per  hour,  not  more,  or  seventy-five  gal- 
lons per  square  foot  in  twenty-four 
hours,  and  that  you  see  is  about  the  rate 
at  which  it  passes  through  these  last 
named  works ;  now  the  effect  at  this 
particular  place  is  that  the  water  is  clari- 
fied, and  a  considerable  proportion  of 
the  organic  matters  in  solution  are  re- 
moved from  it.  The  sand  of  the  surface 
of  the  filter  beds  requires  scraping  from 
time  to  time,  and  also  renewing. 

At  the  Gorbals  Filtration  Works  near 
Glasgow,  the  filtering  materials  are 
placed  in  vertical  compartments  with 
passages  between  them,  in  each  of  which 
the  water  rises  to  nearly  its  original 
level  and  then  flows  over  into  the  next 
compartment  and  down  through  the 
filtering  material  in  it.  There  are  two 
other  plans  I  must  mention;  at  Black- 
burn, for  instance,  there  is  no  filtration. 


133 

There  they  have  a  surface  reservoir,  and 
they  take  the  water  out  of  it  from  the 
top  by  a  sort  of  process  of  decantation. 
They  let  it  settle,  and  then  take  only  the 
water  from  the  top.  Another  plan  is  in 
practice  at  St.  Petersburg.  There  the 
water  is  made  to  fall  down  a  series  of 
steps,  and  then  through  wire  gauze,  and 
lastly  through  sand  niters,  and  by  these 
means  the  water  which  is  generally  very 
impure  is  rendered  tolerably  pure  and  a 
considerable  amount  of  putrescible  or- 
ganic matters  is  collected  from  this  wire 
gauze. 

Now  we  have  to  consider  briefly  the 
ways  in  which  water  may  be  distributed 
in  towns.  In  the  first  place,  as  to  the 
mains :  their  size  must  be  calculated  ac- 
cording to  the  supply  required. 

Mains  are  often  made  in  towns  on 
both  sides  of  the  streets,  in  order  that 
the  supply  may  not  be  entirely  cut  off 
during  repairs.  There  must  be  means 
provided  by  which  the  water  may  be 
stopped  in  a  main  in  order  that  it  may 
be  repaired.  The  bends  and  junctions 


134 

should  always  be  curved.  There  should 
be  no  junctions  made  at  right  angles, 
and  there  should  be  no  angular  junctions 
if  it  can  be  helped.  Mains  should  be 
made  of  cast  iron.  They  should  be 
greater  than  3  inches  in  diameter.  The 
best  service  pipes  for  houses  are  f  in.,  or 
1  inch  wrought  iron  service  pipes  that 
screw  together.  They  are  better  than 
lead,  and  they  are  likewise  cheaper  than 
lead.  Wrought  iron  pipes  are  better 
than  lead  for  this  reason,  that  certain 
kinds  of  water  act  upon  lead.  Soft 
water  is  apt  to  act  upon  lead.  Fortu- 
nately, hard  waters,  containing  a  con- 
siderable amount  of  carbonic  acid,  act 
very  little  on  leaden  pipes,  and  so  it  is 
the  practice  very  frequently  to  have 
leaden  pipes  and  cisterns  made  of  lead, 
and  practically  very  little  harm  results. 
If  you  refer  to  the  25th  vol.  of  the 
"Proceedings  of  the  Institution  of  Civil 
Engineers,"  you  will  find  a  discussion  on 
water  supply,  and  there  you  will  see 
that  Mr.  Bateman  gave  it  as  his  opinion 
that  even  soft  water  acted  very  little 


135 

indeed  on  leaden  pipes,  after  a  time. 
It  acts  on  them  at  first,  but  the  leaden 
pipe  or  cistern  soon  gets  covered  inside 
with  an  insoluble  coat  of  subcarbonate 
of  lead,  and  the  result  is  that  afterwards 
the  water  acts  very  little  on  it.  The 
water  of  Loch  Katrine,  which  is  supplied 
to  Glasgow,  acts  very  little  on  the  lead- 
en pipes  and  cisterns  used.  However, 
there  is  no  reason  for  having  lead  if  dan- 
ger be  apprehended  as  likely  to  result ; 
wrought  iron  will  do  just  as  well,  and  is 
cheaper. 

A  town  may  be  supplied  in  one  of 
two  ways.  These  two  ways  are  known 
as  the  Constant  and  Intermittent  sys- 
tems. First,  there  is  the  Constant  sys- 
tem, in  which,  of  course,  the  mains  are 
always  full,  and  the  water  is  brought 
into  the  houses  by  pipes  from  the  mains, 
no  cisterns  being  needed,  as  the  water  is 
always  in  the  pipes,  and  you  have  only 
to  turn  a  tap  in  order  to  get  it.  Second- 
ly, there  is  the  Intermittent  system,  in 
which  the  water  is  only  supplied  for  a 
short  time  during  the  day,  and  in  this 


136 

Intermittent  system  it  is  therefore  neces- 
sary to  have  cisterns  in  the  houses.  Now 
as  to  the  relative  advantages  and  disad- 
vantages. Professor  Bankine  says : 
"  The  system  called  that  of  Constant  ser- 
vice according  to  which  all  distributing 
pipes  are  kept  charged  with  water  at  all 
times,  is  the  best,  not  only  for  the  con- 
venience of  the  inhabitants,  but  also  for 
the  durability  of  the  pipes  and  for  the 
purity  of  the  water;  for  pipes  when 
alternately  wet  and  dry  tend  to  rust,  and 
when  emptied  of  water  they  are  liable 
to  collect  rust,  dust,  coal-gas  and  the 
effluvia  of  neighboring  sewers,  which 
are  absorbed  by  the  water  on  its  re- 
admission.  In  order,  however,  that  the 
system  of  Constant  service  may  be  car- 
ried out  with  efficiency  and  economy,  it 
is  necessary  that  the  diameters  of  the 
pipes  should  be  carefully  adapted  to 
their  discharge,  and  to  the  elevation  of 
the  district  which  they  are  to  supply, 
and  that  the  town  should  be  sufficiently 
provided  with  town  reservoirs.  When 
these  conditions  are  not  fulfilled,  it  may 


157 

be  indispensable  to  practice  the  system 
of  Intermittent  service,  especially  as  re- 
gards elevated  districts,  that  is  to  say, 
to  supply  certain  districts  in  succession 
during  certain  hours  of  the  day."  You 
see,  therefore,  that  Professor  Rankine 
emphatically  condemns  the  system  of 
Intermittent  service  as  compared  with 
that  of  Constant  service. 

Now  the  great  objection  to  the  system 
of  Intermittent  service  is  the  necessity 
of  having  cisterns,  whatever  they  are 
made  of.  Water  becomes  impure  in  cis- 
terns, dust  collects  in  them,  and  the  cis- 
terns require  frequently  to  be  cleansed. 
If  this  is  not  done  the  water  may  even 
become  dangerous  to  drink.  Where  cis- 
terns are  necessary,  slate  cisterns  are 
the  best.  They  require  to  be  made  with 
good  cement,  or  they  are  apt  to  leak, 
and  then  you  are  liable  to  get  red  lead 
or  something  of  that  sort  used  to  fill  up 
the  joints,  and  so  you  get  the  water 
tainted.  Iron  rusts,  and  for  that  reason 
cast  iron  mains  require  to  be  varnished 
inside  and  out.  Zinc  has  been  used  for 


138 

cisterns  and  also  for  pipes,  but  zinc  often 
contains  lead,  and  cases  have  been  known 
of  lead-poisoning  having  resulted  from 
the  use  of  zinc  pipes  or  cisterns.  There 
have  been  plenty  of  ways  proposed  for 
coating  lead  pipes  so  that  the  water  may 
not  act  upon  them.  Several  of  them  are 
absolutely  objectionable ;  one  of  the 
methods,  for  instance,  was  the  use  of  a 
varnish  containing  arsenic ;  and  even 
other  varnishes,  which  do  not  seem  to  be 
objectionable,  are  not  now  practically 
used. 

If  you  look  in  vols.  12  and  25  of  the 
Proceedings  of  the  Institution  of  Civil 
Engineers,  you  will  see  a  great  many 
arguments  for  and  against  both  the 
"  Constant  "  and  "  Intermittent  "  sys- 
tems, and  one  argument  against  the 
"Intermittent"  system  is  always  that 
the  amount  of  waste  is  enormous.  It  is 
stated,  as  you  will  there  find,  that  at  that 
time  the  amount  of  water  wasted  in  Lon- 
don was  something  like  half  the  supply. 
You  find  it  alleged  that  there  is  great 
waste  also  on  the  Constant  system,  be- 


139 

cause,  it  is  said,  the  mains  are  always 
full  and  the  taps  are  apt  to  be  left 
running.  But  this  may  be  provided 
against  by  having  the  taps  placed  inside 
the  houses,  and  then  you  will  be  quite 
sure  there  is  not  much  waste.  Then,  the 
waste  that  has  been  observed  with  the 
Constant  system  has  been  mostly  caused 
where  the  Intermittent  system  has  been 
changed  for  the  Constant  system,  and  in 
that  case  you  do  sustain  a  loss  of  water; 
a  loss  on  account  chiefly  of  faulty  pipes, 
\  and  leaky  fittings,  for  such  as  may  do 
y  very  well  under  the  Intermittent  system 
are  not  good  enough  to  be  employed  for 
the  Constant  system.  In  Liverpool,  at  a 
particular  date,  there  were  used  33,000,- 
000  gallons  of  water  a  week,  in  the  sup- 
ply of  which  only  1,000,000  gallons 
,  were  supplied  on  the  Constant  service, 
and  the  whole  of  the  remaining  32,000,- 
000  gallons  were  on  the  Intermittent  ser- 
vice. For  some  weeks,  as  an  experi- 
ment, three  sevenths  of  the  town  were 
put  on  the  Constant  service,  and  then 
the  amount  of  water  used  rose  from 


140 

33,000,000  to  41,000,000  gallons  per 
week.  But  where  there  has  originally 
been  sufficient  attention  to  the  fittings, 
and  where  they  are  strong  enough  it  is 
otherwise.  For  instance,  in  the  case  of 
Wolverhampton,  at  the  same  period,  it 
is  stated  that  in  that  town  there  was  a 
saving  effected  by  changing  from  the 
Intermittent  to  the  Constant  system,  a 
saving  of  no  less  than  20  gallons  per 
head  per  day.  (Vol.  xii.,  p.  503.) 

A  disadvantage  of  the  Constant  sys- 
tem is  that  the  water  supply  sometimes 
runs  short  in  the  higher  parts  of  the 
town,  while  in  the  lower  parts  there  is  a 
sufficient  supply;  so  that  cisterns  would 
sometimes  need  to  be  provided,  even 
under  the  Constant  system,  in  these  high- 
er parts  of  the  town. 

As  a  summary :  With  the  Constant 
system  the  waste  of  water  is  certainly 
less  than  with  the  other  if  the  fittings 
are  properly  attended  to,  and  if  the  fit- 
tings, pipes,  etc.,  have  been  originally 
arranged  for  the  Constant  system.  The 
water  in  the  case  of  the  Constant  ser- 


141 

vice  is  purer  and  fresher,  and  at  a  lower 
temperature  in  summer,  and  less  subject 
to  frost  in  winter.  The  water  is  purer 
because  it  escapes  the  impurities  which  I 
have  already  pointed  out,  as  collecting 
in  pipes,  and  it  also  escapes  those  im- 
purities which  the  water  gets  by  being 
stored  in  cisterns. 

The  inconvenience  from  interruption 
to  the  supply  during  repairs  is  never 
actually  experienced,  as  the  interruption 
need  only  be  for  a  few  hours.  On  the 
other  hand,  the  interruptions  and  the 
waste  caused  by  neglect  of  turn-cocks,  by 
the  limitation  of  the  quantity  of  water, 
by  leaky  taps  and  cisterns,  and  in  other 
ways — these  inconveniences  are  absent. 
Then  the  leakage  from  pipes  is  less.  In 
the  Constant  service  the  pipes  are  made 
stronger,  and  practically  there  is  much 
less  bursting.  Mr.  Hawkesley  states 
that  the  difference  between  the  systems 
is  a  question  of  pipes  and  fittings,  and 
that  when  the  supply  is  well  managed 
the  waste  under  the  Constant  system  is 
less. 


142 

Then  the  water  supply  should  always 
be  to  the  top  of  the  house,  and,  if  pos- 
sible, to  each  story  of  the  house.  If  cis- 
terns are  necessary,  those  used  for  drink- 
ing water  should  always  be  separate  from 
any  other  cistern  in  the  house.  If,  for 
instance,  there  is  a  cistern  for  the  water- 
closet,  it  should  be  entirely  separate  from 
the  cistern  used  for  the  storage  of  drink- 
ing water ;  there  should  be  two  separate 
cisterns.  Then  a  chief  point  to  attend 
to  with  regard  to  the  drinking  water 
system  is  that  it  should  be  covered. 
Secondly — That  it  should  be  easily  ac- 
cessible, so  as  to  be  readily  cleaned  out : 
and  thirdly — and  this  is  a  most  important 
point — that  the  waste  pipe  from  it  should 
empty  out  into  the  open  air  either  over 
the  surface  of  the  yard  or  over  a  roof 
or  into  a  rain- water  pipe,  which  itself 
does  not  go  down  into  a  drain.  The 
waste  pipe  should  on  no  consideration  be 
connected  with  any  water-closet  appa 
ratus  or  with  drains.  This  is  almost  in- 
variably done,  and  that  is  why  I  insist  so 
much  on  the  importance  of  this  point. 


143 

I  may  tell  you  that  one  of  the  most  fre- 
quent causes  of  typhoid  fever  in  London 
at  this  moment — of  this  I  have  not  the 
slightest  doubt — is  that  the  waste  pipes 
from  the  drinking  water  cisterns  are  con- 
nected with  some  part  of  the  sewerage 
apparatus,  and  very  often  directly  with 
the  sewers.  The  house  drain,  more  fre- 
quently than  not,  being  unventilated,  the 
waste  pipe  of  the  drinking  water  cistern 
becomes  the  ventilator  of  the  house 
drain,  and  the  foul  air  of  the  house  drain 
goes  up  into  the  space  between  the  sur- 
face of  the  water  and  the  lid  of  the  cis- 
tern, and  is  absorbed,  and  the  result,  in 
many  cases,  as  I  have  frequently  observ- 
ed, has  been  a  severe  attack  of  diarrhea 
through  the  whole  household,  or  else  of 
typhoid  fever,  and  I  have  no  doubt  in 
some  cases  of  cholera  also. 

The  overflow  pipes  from  other  cisterns 
we  need  not  be  so  particular  about,  be- 
cause we  do  not  require  to  drink  the 
water;  but  it  is  just  as  well  that  they 
should  empty  in  a  similar  way  if  pos- 
sible. If  not,  they  may  be  made  to  end 
in  what  is  called  the  D  trap  of  the  water- 


144 

closet.     I   shall   explain    that,   however, 
more  fully  further  on. 

Now  we  have  brought  the  water  into 
the  house — either  into  the  cisterns,  or  it 
may  be  merely  into  the  pipes,  which 
are  kept  constantly  full,  and  which  have 
taps  at  various  levels  inside  the  house. 
When  inside  the  house,  it  may  be  puri- 
fied still  further,  if  necessary,  by  house- 
hold charcoal  filters,  or  by  boiling  and 
then  being  left  to  stand  in  stone  vessels. 
That  is  an  excellent  plan,  and  I  must  tell 
you  here  that  impure  water  may  be  puri- 
fied to  a  very  considerable  extent  by 
making  an  infusion  in  it;  for  instance, 
an  infusion  of  tea.  This  is  very  import- 
ant for  you  to  know  when  you  may  have 
to  drink  water  in  marshy  countries.  A 
great  deal  of  mischief  is  sometimes 
done  by  drinking  water  in  marshy  coun- 
tries, and  this  mischief  may  be  prevented 
by  merely  boiling  it.  That  is  a  very 
good  thing,  but  still  it  is  better,  on  the 
whole,  to  make  a  weak  infusion  of  some- 
thing like  tea,  in  it,  and  that  is  the  sys- 
tem which  has  been  practiced  for  a  thou- 
sand ears  in  China. 


14  DAY  USE 

ETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

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